Papers - Ota, Yasutomo

Enhanced Magneto-Optical Effects in Epsilon-Near-Zero Indium Tin Oxide at Telecommunication Wavelengths

Ikeda K., Liu T., Ota Y., Kobayashi N., Iwamoto S.

Advanced Optical Materials (Advanced Optical Materials)  12 ( 2 )  2024.01

Joint Work

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Epsilon-near-zero (ENZ) materials exhibit near-zero permittivity and induce various intriguing linear and nonlinear optical phenomena. Magneto-optical (MO) effects, which are notoriously weak in the optical domain, have been predicted to be significantly enhanced in ENZ materials, which can facilitate the realization of compact nonreciprocal devices. However, to date, enhanced MO effects have been predominantly observed in effective ENZ media, which are commonly based on complex combinations of photonic nanostructures. It is difficult for these effective media to achieve isotropic ENZ responses, which severely limits their use in the development of ENZ-MO devices. Here, enhanced MO effects in pristine indium tin oxide (ITO) with ENZ properties at technologically important telecommunication wavelengths are demonstrated. MO transmission (reflection) spectroscopy of ITO films with different ENZ wavelengths reveal Faraday (Kerr) rotation peaks around the respective ENZ (EN-one) wavelengths, demonstrating that these observations are due to the intrinsic properties of the ITO materials. The demonstrated mechanism of the MO effect enhancement is universal and can be applied to various ENZ materials, including those incorporating ferromagnetic materials. Native ENZ materials with enhanced MO responses will greatly expand the opportunities for the development of novel nonreciprocal nanophotonic devices, such as on-chip optical isolators and one-way topological waveguides.

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Efficient light couplers to topological slow light waveguides in valley photonic crystals

H Yoshimi, T Yamaguchi, S Ishida, Y Ota, S Iwamoto

Optics Express 32 (4), 6382-6390 (Optics Express)  32 ( 4 ) 6382 - 6390 2024

Joint Work

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We numerically and experimentally demonstrate efficient light couplers between topological slow light waveguides in valley photonic crystals (VPhCs) and wire waveguides. By numerical simulations, we obtained a high coupling efficiency of −0.84 dB/coupler on average in the slow light regime of a group index ng = 10 − 30. Experimentally, we fabricated the couplers in a Si slab and measured the transmitted power of the devices. We realized a high coupling efficiency of approximately −1.2 dB/coupler in the slow light region of ng = 10 − 30, which is close to the result from the numerical simulations. These demonstrations will lay the groundwork for low-loss photonic integrated circuits using topological slow light waveguides.

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Telecom‐Band Quantum Dots Compatible with Silicon Photonics for Photonic Quantum Applications

R Katsumi, Y Ota, M Benyoucef

Advanced Quantum Technologies, 2300423 (Wiley)   2024

Joint Work,  ISSN  2511-9044

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Abstract

Silicon photonics is promising for quantum photonics applications owing to its large‐scale and high‐performance circuitry enabled by complementary‐metal‐oxide‐semiconductor fabrication processes. However, there is a lack of bright single‐photon sources (SPSs) capable of deterministic operation on Si platforms, which largely limits their applications. To this end, on‐Si integration of high‐performance solid‐state quantum emitters, such as semiconductor quantum dots (QDs), is greatly desired. In particular, it is preferable to integrate SPSs emitting at telecom wavelengths for fully leveraging the power of silicon photonics, including efficient chip‐to‐fiber coupling. In this review, recent progress and challenges in the integration of telecom QD SPSs onto silicon photonic platforms are discussed.

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Telecom-Band Quantum Dots Compatible with Silicon Photonics for Photonic Quantum Applications

Katsumi R., Ota Y., Benyoucef M.

Advanced Quantum Technologies (Advanced Quantum Technologies)   2024

Joint Work

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Silicon photonics is promising for quantum photonics applications owing to its large-scale and high-performance circuitry enabled by complementary-metal-oxide-semiconductor fabrication processes. However, there is a lack of bright single-photon sources (SPSs) capable of deterministic operation on Si platforms, which largely limits their applications. To this end, on-Si integration of high-performance solid-state quantum emitters, such as semiconductor quantum dots (QDs), is greatly desired. In particular, it is preferable to integrate SPSs emitting at telecom wavelengths for fully leveraging the power of silicon photonics, including efficient chip-to-fiber coupling. In this review, recent progress and challenges in the integration of telecom QD SPSs onto silicon photonic platforms are discussed.

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Reconfigurable synthetic dimension frequency lattices in an integrated lithium niobate ring cavity

A Balcytis, H Dinh, T Ozawa, Y Ota, G Ren, T Baba, S Iwamoto, A Mitchell, ...

 2024

Joint Work

Micro-transfer-printed membrane lasers on Si platform

Y Maeda, T Aihara, T Fujii, T Hiraki, K Takeda, T Tsuchizawa, H Sugiyama, ...

Novel In-Plane Semiconductor Lasers XXIII 12905, 92-95  2024

Joint Work

Micro-transfer-printed InP-based membrane photonic devices on thin-film lithium niobate platform

Y Maeda, H Nishi, NP Diamantopoulos, T Fujii, T Aihara, S Yamaoka, ...

Journal of Lightwave Technology (Journal of Lightwave Technology)   2024

Joint Work,  ISSN  07338724

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We demonstrate a heterogeneous integration of electrically-pumped membrane lasers and semiconductor optical amplifiers (SOAs) on a thin-film lithium niobate (TFLN) platform by a micro-transfer-printing (μTP) method. Thanks to the low coupling loss (∼1.0 dB) between the InP-based membrane photonic devices and the TFLN waveguides, mW-class output power laser and low-power-consumption SOA on a TFLN platform are achieved. A 128-Gbit/s non-return-to-zero (NRZ) signal modulation is also demonstrated with a TFLN Mach-Zehnder modulator and an integrated membrane laser. These results indicate that the heterogeneous integration of membrane devices using μTP is promising for manufacturing TFLN photonic integrated circuits for optical communications and other applications.

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Hybrid distributed Bragg reflector laser on Si with a transfer printed InAs/GaAs quantum dot amplifier

N Morais, J Fujikata, J Kwoen, T Nakamura, Y Ota, Y Arakawa

Optics Express 32 (3), 4295-4304 (Optics Express)  32 ( 3 ) 4295 - 4304 2024

Joint Work

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We demonstrate a hybrid integrated laser by transfer printing an InAs/GaAs quantum dot (QD) amplifier on a Si waveguide with distributed Bragg reflectors (DBRs). The QD waveguide amplifier of 1.6 mm long was patterned in the form of an airbridge with the help of a spin-on-glass sacrificial layer and precisely integrated on the silicon-on-insulator (SOI) waveguide by pick-and-place assembly using an elastomer stamp. Laser oscillation was observed around the wavelength of 1250 nm with a threshold current of 47 mA at room temperature and stable operation up to 80°C. Transfer printing of the long QD amplifiers will enable the development of various hybrid integrated laser devices that leverage superior properties of QDs as laser gain medium.

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Enhanced Magneto‐Optical Effects in Epsilon‐Near‐Zero Indium Tin Oxide at Telecommunication Wavelengths

K Ikeda, T Liu, Y Ota, N Kobayashi, S Iwamoto

Advanced Optical Materials 12 (2), 2301320  2024

Joint Work

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Valley photonic crystal waveguides fabricated with CMOS-compatible process

T Yamaguchi, H Yoshimi, M Seki, M Ohtsuka, N Yokoyama, Y Ota, ...

Japanese journal of applied physics 62 (8), 082002 (Japanese Journal of Applied Physics)  62 ( 8 )  2023

Joint Work,  ISSN  00214922

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Valley photonic crystal (VPhC) waveguides have attracted much attention because of their ability to enable robust light propagation against sharp bends. However, their demonstration using a CMOS-compatible process suitable for mass production has not yet been reported at the telecom wavelengths. Here, by tailoring the photomask to suppress the optical proximity effect, VPhC patterns comprising equilateral triangular holes were successfully fabricated using photolithography. We optically characterized the fabricated VPhC devices using microscopic optics with NIR imaging. For comparison, we also fabricated and characterized line-defect W1 PhC waveguides, in which the transmission intensities decreased at some regions within the operating bandwidth when sharp turns were introduced into the waveguide. In contrast, the developed VPhC waveguides can robustly propagate light around the C-band telecommunication wavelengths, even in the presence of sharp bends. Our results highlight the potential of VPhC waveguides as an interconnection technology in silicon topological photonic ICs.

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Ultrathin magneto-optical devices based on all-dielectric metasurfaces

Y Ota, S Gao, S Iwamoto

International Conference on Metamaterials, Photonic Crystals and Plasmonics … (International Conference on Metamaterials, Photonic Crystals and Plasmonics)     438 - 439 2023

Joint Work

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Magneto-optical (MO) devices play a key role in introducing nonreciprocity in optical systems, but tend to be bulky due to weak MO effects available in the optical regime. In this talk, we discuss our recent efforts to design of all-dielectric MO metasurfaces toward ultrathin MO devices. We found that large Faraday rotations and high light transmittance can be realized in MO metasurfaces that are much thinner than the operating wavelength.

Topological corner states in photonic bilayer square lattice with π flux

N Ishida, M Ezawa, G Lu, W Lin, Y Ota, Y Arakawa, S Iwamoto

International Conference on Metamaterials, Photonic Crystals and Plasmonics … (International Conference on Metamaterials, Photonic Crystals and Plasmonics)     789 - 790 2023

Joint Work

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We analyzed a bilayer photonic structure consisting of two topologically distinct square lattices with π flux by using a tight-binding model. In the weak interlayer coupling regime, a topological corner state exists at each corner of the finite bilayer lattice, while it disappears when the coupling strength exceeds a critical value, indicating the occurrence of a topological phase transition induced by the interlayer coupling. This phenomenon could be applicable to control light localization in bilayer photonics systems.

Synthetic frequency dimension state coupling in modulated LNOI ring cavity devices

A Balčytis, XH Dinh, T Ozawa, Y Ota, T Baba, S Iwamoto, A Mitchell, ...

2023 Conference on Lasers and Electro-Optics (CLEO), 1-2 (2023 Conference on Lasers and Electro-Optics, CLEO 2023)   2023

Joint Work

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We created a modulatorequipped thinfilm lithium niobate integrated ring resonator simulating a synthetic frequency dimension tightbinding model. It produces frequency states spaced over a 600 GHz bandwidth. Reconfigurable coupling enables simulation of disparate twodimensional interactions.

Supersymmetric non-Hermitian topological interface laser

M Ezawa, N Ishida, Y Ota, S Iwamoto

Physical Review B 107 (8), 085302 (Physical Review B)  107 ( 8 )  2023

Joint Work,  ISSN  24699950

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We investigate laser emission at the interface of the topological and trivial phases in one dimension. The system is described by a generalized Su-Schrieffer-Heeger model with site-dependent hopping parameters involving the interface width parameter where gain (loss) is introduced only to the A (B) sites of the bipartite lattice. The topological interface state is described by the Jackiw-Rebbi state with a pure imaginary energy, reflecting the non-Hermiticity of the system. It feels only the gain effect since it is strictly localized at the A sites. The Jackiw-Rebbi state exists for any value of the interface width. We, thus, obtain a large area single-mode laser by making the interface width wide enough. We also find a series of analytic solutions of excited states based on supersymmetry (SUSY) quantum mechanics where the A and B sites of the bipartite lattice form SUSY partners. Furthermore, we study the system containing loss and gain with saturation by extending the Jackiw-Rebbi mode to a nonlinear theory.

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Slow light waveguide based on semiconductor valley photonic crystal

S Iwamoto, H Yoshimi, K Kuruma, R Miyazaki, Y Ota

Plasmonics: Design, Materials, Fabrication, Characterization, and …  2023

Joint Work

Realization of large magneto-optical effect by diagonal permittivity change in epsilon-near-zero materials

K Ikeda, T Liu, Y Ota, S Iwamoto, N Kobayashi

2023 IEEE International Magnetic Conference-Short Papers (INTERMAG Short … (2023 IEEE International Magnetic Conference - Short Papers, INTERMAG Short Papers 2023 - Proceedings)   2023

Joint Work

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The Epsilon near-zero (ENZ) effect has been suggested as a method to enhance the magneto-optical (MO) effect; however, the enhancement of the MO effect in the ENZ materials has not been experimentally verified. Here, we measured the MO properties of ENZ materials and analyzed the correlation between the diagonal permittivity and MO effect. The Faraday effect is enhanced in the wavelengths where the real part of diagonal permittivity is almost zero and the Kerr effect is enhanced in the wavelengths where the diagonal permittivity is almost one. Our findings would lead to various potential applications, including on-chip isolators and one-way topological waveguides.

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Optimizing the optical and magneto-optical response of all-dielectric metasurfaces with tilted side walls

S Gao, Y Ota, F Tian, T Liu, S Iwamoto

Optics Express 31 (9), 13672-13682 (Optics Express)  31 ( 9 ) 13672 - 13682 2023

Joint Work

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All-dielectric metasurfaces based on ferrimagnetic iron garnets are a promising platform for realizing ultra-compact magneto-optical (MO) devices with low loss. However, ferrimagnetic iron garnets are notorious for being intractable on fine nanopatterning, hindering the faithful fabrication of designed nanostructures. In this regard, it is important to assess the influence of fabrication imperfections on the performance of MO metasurfaces. Here, we investigate the optical properties of a MO metasurface with structural imperfections. As the most typical fabrication error, we studied the impact of the tilted side walls of cylindrical garnet disks that constitute the metasurfaces. We found that tilting the side walls drastically degrades the MO response and light transmittance of the device. Nevertheless, it was also found that the performance can be recovered by optimizing the refractive index of the material covering the upper half of the nanodisks.

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Nonadiabatic nonlinear non-Hermitian quantized pumping

M Ezawa, N Ishida, Y Ota, S Iwamoto

arXiv preprint arXiv:2310.17987  2023

Joint Work

Micro-transfer-printed membrane distributed reflector lasers on Si waveguide modulated with 50-Gbit/s NRZ signal

Y Maeda, T Aihara, T Fujii, T Hiraki, K Takeda, T Tsuchizawa, H Sugiyama, ...

Journal of Lightwave Technology 41 (12), 3866-3873 (Journal of Lightwave Technology)  41 ( 12 ) 3866 - 3873 2023

Joint Work,  ISSN  07338724

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In this work, we fabricate directly modulated membrane distributed reflector (DR) lasers on a Si waveguide by utilizing micro-transfer printing method. Micro-transfer printing enables low-loss coupling between the lasers and the silicon photonics circuit, and since it is a back-end process, we can test the lasers prior to integration. A membrane laser is as thick as the Si waveguides, which makes optical coupling between the two quite easy. In addition, membrane lasers with a lateral p-i-n diode structure have low capacitance and a large optical confinement factor, which means they can achieve a low threshold current and high-speed modulation operation with low energy consumption. The fabricated membrane DR laser integrated with a 220-nm-thick Si waveguide exhibits a low threshold current of 1.2 mA and single-mode operation at 1535 nm with a side-mode suppression ratio (SMSR) of about 40 dB at the bias current of 14 mA. It also achieves the E-O bandwidth of over 25 GHz and 50-Gbit/s non-return-to-zero (NRZ) signal modulation with an extinction ratio of 2.5 dB.

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Magneto-optical material and production method therefor

S Iwamoto, Y Ota, K Ikeda, N Kobayashi

US Patent App. 18/019,317  2023

Joint Work

High-Q two-dimensional photonic crystal nanocavity on glass with an upper glass thin film

R Kawata, A Fujita, N Pholsen, S Iwamoto, Y Ota

arXiv preprint arXiv:2311.00935  2023

Joint Work

Faraday rotator based on a silicon photonic crystal slab on a bismuth-substituted yttrium iron garnet thin film

S Gao, Y Ota, T Liu, F Tian, S Iwamoto

Applied Physics Express 16 (7), 072003 (Applied Physics Express)  16 ( 7 )  2023

Joint Work,  ISSN  18820778

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We report the design of an ultrathin Faraday rotator consisting of a silicon photonic crystal (PhC) slab on a bismuth-substituted yttrium iron garnet (Bi:YIG) thin film. By directing light into guided modes in the Bi:YIG layer via diffraction in the PhC layer, we numerically demonstrate a Faraday rotation angle of ∼45° at a telecom wavelength with a Bi:YIG layer thickness of only ∼500 nm. This structure permits a high light transmittance of about 70%, enabled by electromagnetically induced transparency. The proposed design only requires nanopatterning of the Si layer, providing a viable route to practical ultrathin Faraday rotators.

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Topologically-Protected Single-Photon Sources with Topological Slow Light Photonic Crystal Waveguides

Kuruma K., Yoshimi H., Ota Y., Katsumi R., Kakuda M., Arakawa Y., Iwamoto S.

Laser and Photonics Reviews (Laser and Photonics Reviews)  16 ( 8 )  2022.08

Joint Work,  ISSN  18638880

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Slow light waveguides are advantageous for implementing high-performance single-photon sources required for scalable operation of integrated quantum photonic circuits (IQPCs), though such waveguides are known to suffer from propagation loss due to backscattering. A way to overcome the drawback is to use topological photonics, in which robust waveguiding in topologically-protected optical modes has recently been demonstrated. Here, single-photon sources are reported using single quantum dots (QDs) embedded in topological slow light waveguides based on valley photonic crystals. Purcell-enhanced single-photon emission is demonstrated from a QD into a topological slow light mode with a group index over 20 and its robust propagation even under the presence of sharp bends. These results pave the way for the realization of robust and high-performance single-photon sources indispensable for IQPCs.

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Topological Band Gaps Enlarged in Epsilon-Near-Zero Magneto-Optical Photonic Crystals

T Liu, N Kobayashi, K Ikeda, Y Ota, S Iwamoto

ACS Photonics (American Chemical Society (ACS))  9 ( 5 ) 1621 - 1626 2022

Joint Work,  ISSN  2330-4022

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Topological photonics provides exciting and emerging opportunities for the manipulation of light. As the photonic analogue of quantum Hall edge states, chiral edge modes, arising at the interface between two photonic topological structures with different Chern numbers, hold great promise for robust transport of light against disorders and defects. However, for magneto-optical material-based topological photonic crystals, the transport performance of chiral edge modes is strongly dependent on the topological gap sizes, which are usually very narrow at optical frequencies due to the lack of magneto-optical materials with strong nonreciprocal responses. Here, we numerically demonstrated that the introduction of an epsilon-near-zero effect to magneto-optical photonic crystals could remarkably enlarge topological gap sizes due to the boosted magneto-optical response. Eigenmode calculation results show that the boosted magneto-optical response correlates to the enhanced nonreciprocal power flows in magnetized photonic crystals with an epsilon-near-zero diagonal permittivity. The enlarged topological band gap leads to the broadband and well-confined chiral edge modes propagating along the magnetized boundary between two oppositely magnetized photonic crystals. More importantly, such mode propagation shows strong robustness against sharp bends and large defects. In principle, our proposal for the enlargement of topological photonic band gaps could also be valid in photonic crystal slabs or even three-dimensional photonic crystals. Our results not only suggest the possibility to improve the transport performance of one-way modes in magneto-optical photonic crystals but also enrich the physical understanding of the epsilon-near-zero effect-based topological photonics.

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CMOS-compatible integration of telecom band InAs/InP quantum-dot single-photon sources on a Si chip using transfer printing

R Katsumi, Y Ota, T Tajiri, S Iwamoto, K Ranbir, JP Reithmaier, ...

Applied Physics Express 16 (1), 012004 (IOP Publishing)  16 ( 1 ) 012004 - 012004 2022

Joint Work,  ISSN  1882-0778

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Abstract

We report the hybrid integration of a telecom band InAs/InP quantum-dot (QD) single-photon source on a CMOS-processed Si photonics chip using transfer printing. The integration technique allows for the assembly of photonic components in a pick-and-place operation and therefore can introduce them on Si photonics chips after completing the entire CMOS-compatible fabrication processes. We demonstrate telecom single-photon generation from an InAs/InP QD integrated on Si and its coupling into a waveguide. We also demonstrate the integration of a QD on a fiber-pigtailed Si chip and single-photon output through the optical fiber, showing a novel pathway for modularizing solid-state quantum light sources.

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Topologically‐protected single‐photon sources with topological slow light photonic crystal waveguides

K Kuruma, H Yoshimi, Y Ota, R Katsumi, M Kakuda, Y Arakawa, ...

Laser & Photonics Reviews 16 (8), 2200077 (Wiley)  16 ( 8 ) 2200077 - 2200077 2022

Joint Work,  ISSN  1863-8880

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Topological modes observed in Si photonics SSH integrated circuit

R Nakamura, T Nakama, A Balčytis, T Ozawa, Y Ota, S Iwamoto, H Ito, ...

Conference on Lasers and Electro-Optics/Pacific Rim, CThA8D_02 (Optics InfoBase Conference Papers)   2022

Joint Work

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We fabricated a sophisticated Si photonic integrated circuit for investigating topological photonics SSH model. In the selective excitation and observation of SSH coupled microrings, we observed the wavefunctions of edge and bulk modes.

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Semiconductor topological nanophotonics incorporating light emitters

Y Ota, Y Arakawa, S Iwamoto

International Conference on Metamaterials, Photonic Crystals and Plasmonics … (International Conference on Metamaterials, Photonic Crystals and Plasmonics)     412 - 413 2022

Joint Work

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Topological photonic crystals made of compound semiconductors are a fascinating platform to develop topological nanophotonic devices with active functionalities. In this contribution, will discuss recent progress in IIIV-semiconductor topological nanophotonics incorporating optical gain media and quantum emitters. We will review several ways to realize topological nanocavities and topological slow light waveguides, both of which can significantly enhance light-matter interactions with embedded light emitters. These photonic structures enable the realization of topological nano/microlasers and quantum light sources capable of robust operation.

Micro-transfer-printed membrane DR lasers on Si waveguide modulated with 50-Gbit/s NRZ signal

Y Maeda, T Fujii, T Aihara, T Hiraki, K Takeda, T Tsuchizawa, H Sugiyama, ...

European Conference and Exhibition on Optical Communication, We1E. 4 (2022 European Conference on Optical Communication, ECOC 2022)   2022

Joint Work

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We fabricate directly modulated membrane distributed reflector lasers on a Si waveguide by using the micro-transfer printing. A low threshold current of 1.2 mA and good optical coupling between the laser output and 220-nm-thick Si waveguides are achieved. 50-Gbit/s NRZ signal modulation is also demonstrated.

Intrinsically chiral modes near exceptional points in modified H1 photonic crystal cavity modes

CF Fong, Y Ota, Y Arakawa, S Iwamoto, YK Kato

2022 Conference on Lasers and Electro-Optics (CLEO), 1-2  2022

Joint Work

Intrinsically chiral modes near exceptional points in modified H1 photonic crystal cavity modes

Fong C.F., Ota Y., Arakawa Y., Iwamoto S., Kato Y.K.

Optics InfoBase Conference Papers (Optics InfoBase Conference Papers)   2022

Joint Work

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We propose a scheme to generate intrinsically chiral modes via non-Hermitian backscattering caused by the loss-induced imaginary coupling between the two orthogonal linearly polarized dipole modes in the H1 photonic crystal cavity.

Intrinsically chiral modes near exceptional points in modified H1 photonic crystal cavity modes

Fong C.F., Ota Y., Arakawa Y., Iwamoto S., Kato Y.K.

2022 Conference on Lasers and Electro-Optics, CLEO 2022 - Proceedings (2022 Conference on Lasers and Electro-Optics, CLEO 2022 - Proceedings)   2022

Joint Work

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We propose a scheme to generate intrinsically chiral modes via non-Hermitian backscattering caused by the loss-induced imaginary coupling between the two orthogonal linearly polarized dipole modes in the H1 photonic crystal cavity.

Hybrid Integration of Quantum-Dot Non-classical Light Sources on Si

R Katsumi, Y Ota, S Iwamoto, Y Arakawa

Progress in Nanophotonics 7, 93-121 (Topics in Applied Physics)  147   93 - 121 2022

Joint Work,  ISSN  03034216

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This chapter describes the hybrid integration of quantum-dot single-photon sources (QD SPSs) on Si toward the scalable Si quantum photonics. In this study, transfer printing (TP) has been extensively investigated, a technique that simply relies on pick-and-place integration based on van der Waals force, and thus is fully compatible with the CMOS back-end process to exploit mature CMOS technology. Using TP, QD SPSs were hybrid integrated on a CMOS Si chip. It was confirmed that the integrated QDs can generate single photons on a CMOS Si chip. We also observed efficient waveguide coupling of emitted single photons. Furthermore, we extended our TP method for investigating the multiple identical SPSs hybrid integrated on Si. We believe that our TP-based approach will provide a novel pathway toward the scalable implementation of multiple identical QD SPSs on the same CMOS Si chip.

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High-temperature operation of membrane DR lasers integrated with Si waveguide by micro-transfer printing method

Y Maeda, T Aihara, T Fujii, T Hiraki, K Takeda, T Tsuchizawa, H Sugiyama, ...

2022 28th International Semiconductor Laser Conference (ISLC), 1-2 (Conference Digest - IEEE International Semiconductor Laser Conference)  2022-October 2022

Joint Work,  ISSN  08999406

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We fabricate a membrane distributed-reflector lasers with a Si waveguide by using micro-transfer printing, achieving a low threshold current of 1.1-3.7 mA in a temperature range of 25-80 C and good optical coupling between the laser output and 220-nm-thick Si waveguides.

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Generation of Optical Skyrmion Crystal Beams using Polarization-Controlled Coupled-Cavity Systems

W LIN, S IWAMOTO, Y OTA

村田学術振興財団年報, 495-502  2022

Joint Work

Exceptional-point encirclement in an integrated non-Hermitian optomechanical system

Tian F., Ota Y., Iwamoto S.

Optics InfoBase Conference Papers (Optics InfoBase Conference Papers)   2022

Joint Work

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We propose and numerically demonstrate an integrated non-Hermitian optomechanical system capable of exceptional-point encirclement in a deterministic manner. The proposed scheme opens a way for investigating non-Hermitian optomechanics on chip.

Exceptional-point encirclement in an integrated non-Hermitian optomechanical system

Tian F., Ota Y., Iwamoto S.

2022 Conference on Lasers and Electro-Optics, CLEO 2022 - Proceedings (2022 Conference on Lasers and Electro-Optics, CLEO 2022 - Proceedings)   2022

Joint Work

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We propose and numerically demonstrate an integrated nonHermitian optomechanical system capable of exceptionalpoint encirclement in a deterministic manner. The proposed scheme opens a way for investigating nonHermitian optomechanics on chip.

Exceptional-point encirclement in an integrated non-Hermitian optomechanical system

F Tian, Y Ota, S Iwamoto

CLEO: Applications and Technology, JTh3A. 64  2022

Joint Work

Design of an All-dielectric Magneto-optical Metasurface with Giant Faraday Effect and High Light Transmission

S Gao, Y Ota, T Liu, S Iwamoto

Conference on Lasers and Electro-Optics/Pacific Rim, CFA8G_02 (Optics InfoBase Conference Papers)   2022

Joint Work

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We design an all-dielectric metasurface exhibiting giant enhancement of magneto-optical Faraday rotation and high light transmission. A 760-times larger Faraday rotation than that in the unprocessed host material of the same thickness was numerically observed.

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Design of a Quantum-Dot Single-Photon Source on a Silicon Nitride Waveguide for Efficient Photon Generation by Resonant Excitation

N Pholsen, Y Ota, S Iwamoto

2022 28th International Semiconductor Laser Conference (ISLC), 1-2 (Conference Digest - IEEE International Semiconductor Laser Conference)  2022-October 2022

Joint Work,  ISSN  08999406

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We design a quantum-dot single-photon source with a defect-based photonic crystal cavity on a SiN waveguide that subdues crosstalk from resonant excitation and has >90% coupling efficiency. It is expected to efficiently generate single photons with high purity and indistinguishability for scalable integrated quantum photonics.

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Design of a quantum-dot single-photon source on a silicon nitride waveguide for efficient and indistinguishable photon generation

Pholsen N., Ota Y., Katsumi R., Arakawa Y., Iwamoto S.

Optics InfoBase Conference Papers (Optics InfoBase Conference Papers)   2022

Joint Work

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We design quantum-dot single-photon sources based on a defect-based photonic crystal cavity on a SiN waveguide with >90% efficiency. The defect region secures distance between etched airholes and quantum dots, expected to improve photon indistinguishability.

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Design of a quantum-dot single-photon source on a silicon nitride waveguide for efficient and indistinguishable photon generation

Pholsen N., Ota Y., Katsumi R., Arakawa Y., Iwamoto S.

2022 Conference on Lasers and Electro-Optics Pacific Rim, CLEO-PR 2022 - Proceedings (2022 Conference on Lasers and Electro-Optics Pacific Rim, CLEO-PR 2022 - Proceedings)   2022

Joint Work

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We design quantum-dot single-photon sources based on a defect-based photonic crystal cavity on a SiN waveguide with >90% efficiency. The defect region secures distance between etched airholes and quantum dots, expected to improve photon indistinguishability.

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Design of a quantum-dot single-photon source on a silicon nitride waveguide for efficient and indistinguishable photon generation

N Pholsen, Y Ota, R Katsumi, Y Arakawa, S Iwamoto

Conference on Lasers and Electro-Optics/Pacific Rim, P_CTu8_22  2022

Joint Work

Demonstration of on-chip optical skyrmionic beam generators

W Lin, Y Ota, Y Arakawa, S Iwamoto

CLEO: Science and Innovations, SM2N. 4  2022

Joint Work

Demonstration of On-Chip Optical Skyrmionic Beam Generators

Lin W., Ota Y., Arakawa Y., Iwamoto S.

Optics InfoBase Conference Papers (Optics InfoBase Conference Papers)   2022

Joint Work

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We experimentally demonstrate on-chip optical skyrmionic beam generators. Skyrmionic beams with tailored skyrmion numbers were generated from single silicon mi-crorings diffracting two beams whose spin and orbital angular momenta were controlled via optical spin-orbit coupling.

Demonstration of On-Chip Optical Skyrmionic Beam Generators

Lin W., Ota Y., Arakawa Y., Iwamoto S.

2022 Conference on Lasers and Electro-Optics, CLEO 2022 - Proceedings (2022 Conference on Lasers and Electro-Optics, CLEO 2022 - Proceedings)   2022

Joint Work

　View Summary

We experimentally demonstrate on-chip optical skyrmionic beam generators. Skyrmionic beams with tailored skyrmion numbers were generated from single silicon microrings diffracting two beams whose spin and orbital angular momenta were controlled via optical spin-orbit coupling.

Microcavity-based generation of full Poincare beams with arbitrary skyrmion numbers

Lin Wenbo, Ota Yasutomo, Arakawa Yasuhiko, Iwamoto Satoshi

PHYSICAL REVIEW RESEARCH (American Physical Society (APS))  3 ( 2 )  2021.04

Research paper (scientific journal), Joint Work, Accepted

　View Summary

A full Poincar\'e (FP) beam possesses all possible optical spin states in its
cross-section, which constitutes an optical analogue of a skyrmion. Until now,
FP beams have been exclusively generated using bulk optics. Here, we propose a
generation scheme of an FP beam based on an optical microring cavity. We
position two different angular gratings along with chiral lines on a microring
cavity and generate an FP beam as a superposition of two light beams with
controlled spin and orbital angular momenta. We numerically show that FP beams
with tailored skyrmion numbers can be generated from this device, opening a
route for developing compact light sources with unique optical spin fields.

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Recent progress in topological waveguides and nanocavities in a semiconductor photonic crystal platform [Invited]

Iwamoto Satoshi, Ota Yasutomo, Arakawa Yasuhiko

OPTICAL MATERIALS EXPRESS (The Optical Society)  11 ( 2 ) 319 - 337 2021.02

Research paper (scientific journal), Joint Work, Accepted,  ISSN  2159-3930

　View Summary

Topological photonics provides a novel route for designing and realizing optical devices with unprecedented functionalities. Topological edge states, which are supported at the boundary of two photonic systems with different band topologies, enable robust light transport immune to structural imperfections and/or sharp bends in waveguides. Furthermore, the topological edge states are expected to revolutionize cavity-based optical devices such as lasers. Optical devices with built-in topological protection with a small footprint are fascinating as on-chip optical devices for low-loss and functional photonic integrated circuits. Semiconductor photonic crystals are promising platforms enabling the miniaturization of topological optical devices. Herein, we review the recent realizations of semiconductor topological photonic crystals. In particular, we discuss topological waveguides in valley photonic crystals, which have received increasing attention because of their simple realization. In addition, we provide recent demonstrations of topological nanocavities, which are another key component of topological nanophotonics. Progress in semiconductor topological photonic crystals will propel the use of topological photonic devices in various applications as well as deepen the understanding of topological photonic phenomena at the wavelength scale.

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Experimental demonstration of topological slow light waveguides in valley photonic crystals

H Yoshimi, T Yamaguchi, R Katsumi, Y Ota, Y Arakawa, S Iwamoto

Optics Express 29 (9), 13441-13450 (The Optical Society)  29 ( 9 ) 13441 - 13450 2021

Research paper (scientific journal), Joint Work, Accepted,  ISSN  1094-4087

　View Summary

We experimentally demonstrate topological slow light waveguides in valley photonic crystals (VPhCs). We employed a bearded interface formed between two topologically-distinct VPhCs patterned in an air-bridged silicon slab. The interface supports both topological and non-topological slow light modes below the light line. By means of optical microscopy, we observed light propagation in the topological mode in the slow light regime with a group index ng over 30. Furthermore, we confirmed light transmission via the slow light mode even under the presence of sharp waveguide bends. In comparison between the topological and non-topological modes, we found that the topological mode exhibits much more efficient waveguiding than the trivial one, demonstrating topological protection in the slow light regime. This work paves the way for exploring topological slow-light devices compatible with existing photonics technologies.

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Recent progress in topological waveguides and nanocavities in a semiconductor photonic crystal platform

S Iwamoto, Y Ota, Y Arakawa

Optical Materials Express 11 (2), 319-337  2021

Research paper (scientific journal), Joint Work, Accepted

Unidirectional output from a quantum-dot single-photon source hybrid integrated on silicon

R Katsumi, Y Ota, T Tajiri, M Kakuda, S Iwamoto, H Akiyama, Y Arakawa

arXiv preprint arXiv:2108.04450 (The Optical Society)  29 ( 23 ) 37117 - 37127 2021

Research paper (scientific journal), Joint Work, Accepted,  ISSN  1094-4087

　View Summary

We report a quantum-dot single-photon source (QD SPS) hybrid integrated on a silicon waveguide embedding a photonic crystal mirror, which reflects photons and enables efficient unidirectional output from the waveguide. The silicon waveguide is constituted of a subwavelength grating so as to maintain the high efficiency even under the presence of stacking misalignment accompanied by hybrid integration processes. Experimentally, we assembled the hybrid photonic structure by transfer printing and demonstrated single-photon generation from a QD and its unidirectional output from the waveguide. These results point out a promising approach toward scalable integration of SPSs on silicon quantum photonics platforms.

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Time-resolved physical spectrum in cavity quantum electrodynamics

M Yamaguchi, A Lyasota, T Yuge, Y Ota

arXiv preprint arXiv:2109.02287 (American Physical Society ({APS}))  4 ( 2 )  2021

Research paper (scientific journal), Joint Work, Accepted,  ISSN  26431564

　View Summary

The time-resolved physical spectrum of luminescence is theoretically studied
for a standard cavity quantum electrodynamics system. In contrast to the power
spectrum for the steady state, the correlation functions up to the present time
are crucial for the construction of the time-resolved spectrum, while the
correlations with future quantities are inaccessible because of the causality,
i.e., the future quantities cannot be measured until the future comes. We find
that this causality plays a key role to understand the time-resolved spectrum,
in which the Rabi doublet can never be seen during the time of the first peak
of the Rabi oscillation. Furthermore, the causality can influence on the
transient magnitude of the Rabi doublet in some situations. We also study the
dynamics of the Fano anti-resonance, where the difference from the Rabi doublet
can be highlighted.

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Synthetic Dimension Photonics on a Si CMOS Platform

A Balčytis, T Ozawa, Y Ota, S Iwamoto, J Maeda, T Baba

CLEO: Science and Innovations, STu1F. 4 (Optics InfoBase Conference Papers)   2021

Research paper (scientific journal), Joint Work, Accepted

　View Summary

We present a dynamically modulated ring resonator on a Si CMOS platform, hosting a synthetic dimension lattice over 180 GHz. The frequency and time domain synthetic band structure was acquired and photonic transport phenomena were explored.

Synthetic dimension band structures on a Si CMOS photonic platform

A Balčytis, T Ozawa, Y Ota, S Iwamoto, J Maeda, T Baba

arXiv preprint arXiv:2105.13742 (American Association for the Advancement of Science ({AAAS}))  8 ( 4 ) eabk0468 2021

Research paper (scientific journal), Joint Work, Accepted

　View Summary

Synthetic dimensions, which simulate spatial coordinates using non-spatial
degrees of freedom, are drawing interest in topological science and other
fields for modelling higher-dimensional phenomena on simple structures. We
present the first realization of a synthetic frequency dimension on a silicon
ring resonator photonic device fabricated using a CMOS process. We confirm that
its coupled modes correspond to a 1D tight-binding model through acquisition of
up to 280 GHz bandwidth optical frequency comb-like spectra, and by measuring
the first synthetic band structures on an integrated device. Furthermore, we
realized two types of gauge potentials along the frequency dimension, and
probed their effects through the associated band structures. An electric field
analogue was produced via modulation detuning, whereas effective magnetic
fields were induced using synchronized nearest- and second-nearest-neighbor
coupling. Creation of coupled mode lattices and two effective forces on a
monolithic Si CMOS device represents a key step towards wider adoption of
topological principles.

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Single photon generation in a topological slow light waveguide

K Kuruma, H Yoshimi, Y Ota, R Katsumi, M Kakuda, M Lončar, Y Arakawa, ...

CLEO: QELS_Fundamental Science, FW4I. 2 (OSA)   2021

Research paper (scientific journal), Joint Work, Accepted

　View Summary

We report a topologically-protected single photon source in a slow light waveguide based on valley photonic crystals. Purcell-enhanced single photon generation from a quantum dot and its robust propagation in the topological waveguide are demonstrated.

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Microcavity-based generation of full Poincaré beams with arbitrary skyrmion numbers

W Lin, Y Ota, Y Arakawa, S Iwamoto

Physical Review Research 3 (2), 023055  2021

Research paper (scientific journal), Joint Work, Accepted

Chiral modes near exceptional points in symmetry broken H1 photonic crystal cavities

CF Fong, Y Ota, Y Arakawa, S Iwamoto, YK Kato

arXiv preprint arXiv:2107.14435 (American Physical Society (APS))  3 ( 4 )  2021

Research paper (scientific journal), Joint Work, Accepted,  ISSN  26431564

　View Summary

The H1 photonic crystal cavity supports two degenerate dipole modes of orthogonal linear polarization which could give rise to circularly polarized fields when driven with a π/2 phase difference. However, fabrication errors tend to break the symmetry of the cavity, which lifts the degeneracy of the modes, rendering the cavity unsuitable for supporting circular polarization. We demonstrate numerically a scheme that induces chirality in the cavity modes, thereby achieving a cavity that supports intrinsic circular polarization. By selectively modifying two air holes around the cavity, the dipole modes could interact via asymmetric coherent backscattering, which is a non-Hermitian process. With suitable air hole parameters, the cavity modes approach the exceptional point, coalescing in frequencies and linewidths as well as giving rise to significant circular polarization close to unity. The handedness of the chirality can be selected depending on the choice of the modified air holes. Our results highlight the prospect of using the H1 photonic crystal cavity for chiral light-matter coupling in applications such as valleytronics, spin-photon interfaces, and the generation of single photons with well-defined spins.

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A large-scale single-mode array laser based on a topological edge mode

N Ishida, Y Ota, W Lin, T Byrnes, Y Arakawa, S Iwamoto

arXiv preprint arXiv:2108.11901 (Nanophotonics)  11 ( 9 ) 2169 - 2181 2021

Research paper (scientific journal), Joint Work, Accepted,  ISSN  2192-8606

　View Summary

Topological lasers have been intensively investigated as a strong candidate
for robust single-mode lasers. A typical topological laser employs a
single-mode topological edge state, which appears deterministically in a
designed topological bandgap and exhibits robustness to disorder. These
properties seem to be highly attractive in pursuit of high power lasers capable
of single mode operation. In this paper, we theoretically analyze a large-scale
single-mode laser based on a topological edge state. We consider a sizable
array laser consisting of a few hundreds of site resonators, which support a
single topological edge mode broadly distributed among the resonators. We build
a basic model describing the laser using the tight binding approximation and
evaluate the stability of single mode lasing based on the threshold gain
difference $\Delta\alpha$ between the first-lasing edge mode and the
second-lasing competing bulk mode. Our calculations demonstrate that stronger
couplings between the cavities and lower losses are advantageous for achieving
stable operation of the device. When assuming an average coupling of 100
cm$^{-1}$ between site resonators and other realistic parameters, the threshold
gain difference $\Delta\alpha$ can reach about 2 cm$^{-1}$, which would be
sufficient for stable single mode lasing using a conventional semiconductor
laser architecture. We also consider the effects of possible disorders and
long-range interactions to assess the robustness of the laser under non-ideal
situations. These results lay the groundwork for developing single-mode
high-power topological lasers.

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Two-dimensional Topological Photonic Crystals with Helical Edge States below the Light Line

C Zhang, H Yoshimi, Y Ota, S Iwamoto

2021 26th Microoptics Conference (MOC), 1-2 (26th Microoptics Conference, MOC 2021)   2021

Joint Work

　View Summary

We design semiconductor-based two-dimensional photonic crystals that can support topological helical edge states below the light line. We numerically demonstrate that the edge states can guide light robustly in the waveguide even with sharp bends. The structure will be a new platform for topological nanophotonic waveguides with no radiation loss.

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Topologically-protected single-photon sources in topological slow light photonic crystal waveguides

K Kuruma, H Yoshimi, Y Ota, R Katsumi, M Kakuda, Y Arakawa, ...

arXiv preprint arXiv:2112.10317  2021

Joint Work

Topological nanophotonics and topological lasers

Y Ota, Y Arakawa, S Iwamoto

JSAP-OSA Joint Symposia, 13a_N404_7 (Optics InfoBase Conference Papers)   2021

Joint Work

Semiconductor Topological Nanophotonics

Y Ota, Y Arakawa, S Iwamoto

2021 IEEE International Electron Devices Meeting (IEDM), 38.5. 1-38.5. 4 (Technical Digest - International Electron Devices Meeting, IEDM)  2021-December   38.5.1 - 38.5.4 2021

Joint Work,  ISSN  01631918

　View Summary

We will discuss possible applications of topological photonics to photonic integrated circuit technologies. We design nanophotonic elements based on topological edge states emerging at the exteriors of bulk structures and apply them to compact semiconductor lasers and waveguides. Such topological photonic devices are known to be immune to fabrication imperfections and therefore are suitable for building robust optical circuitry. We also address the idea of topological high-power lasers that take advantage of topological edge states for robust single mode lasing.

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One-side excited one-way modes in nonreciprocal waveguides

T Liu, Y Ota, S Iwamoto

JSAP-OSA Joint Symposia, 10p_N404_5 (Optics InfoBase Conference Papers)   2021

Joint Work

Intrinsic circularly polarized H1 photonic crystal cavity modes near exceptional points

CF Fong, Y Ota, Y Arakawa, S Iwamoto, YK Kato

JSAP-OSA Joint Symposia, 10p_N404_7 (Optics InfoBase Conference Papers)   2021

Joint Work

Hybrid integrated light sources on silicon assembled by transfer printing

Y Ota, S Iwamoto, Y Arakawa

2021 IEEE Photonics Conference (IPC), 1-2 (2021 IEEE Photonics Conference, IPC 2021 - Proceedings)   2021

Joint Work

　View Summary

We will discuss the hybrid integration of micro/nanoscale light sources on silicon photonics circuits with transfer printing, which is based on pick-and-place assembly using a viscoelastic stamp. Various light sources including quantum-dot single-photon sources are readily and flexibly integrated on silicon with high positioning accuracy.

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Fabrication of valley photonic crystals with CMOS-compatible process

T Yamaguchi, H Yoshimi, M Seki, M Ohtsuka, N Yokoyama, Y Ota, ...

2021 26th Microoptics Conference (MOC), 1-2 (26th Microoptics Conference, MOC 2021)   2021

Joint Work

　View Summary

We demonstrated the fabrication of silicon valley photonic crystal structures with triangular air holes by using photolithography for the first time. The mask patterns we newly designed enable the formation of triangular air holes with reasonably high accuracy. This is an important step toward CMOS-compatible topological nanophotonics.

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Design of a defect-based photonic crystal nanobeam cavity robustly coupled to an underlying SiN waveguide

N Pholsen, Y Ota, R Katsumi, Y Arakawa, S Iwamoto

JSAP Annual Meetings Extended Abstracts The 68th JSAP Spring Meeting 2021 …  2021

Joint Work

Si CMOS ring resonator device for synthetic dimension photonics

A Balcytis, T Ozawa, Y Ota, S Iwamoto, J Maeda, T Baba

JSAP Annual Meetings Extended Abstracts The 68th JSAP Spring Meeting 2021 …  2021

Joint Work

Investigation of enlarged topological band gaps in magneto-optical epsilon-near-zero photonic crystals

T Liu, N Kobayashi, K Ikeda, Y Ota, S Iwamoto

JSAP Annual Meetings Extended Abstracts The 68th JSAP Spring Meeting 2021 …  2021

Joint Work

Efficient single photon sources transfer-printed on Si with unidirectional light output

R Katsumi, Y Ota, T Tajiri, M Kakuda, S Iwamoto, H Akiyama, Y Arakawa

CLEO: QELS_Fundamental Science, FF2D. 3 (OSA)  2020-May 2020

Research paper (scientific journal), Joint Work, Accepted,  ISSN  2160-9020

　View Summary

We report efficient quantum-dot single-photon sources with unidirectional output integrated on Si by transfer printing. The device was designed to be robust against misalignment accompanied by the hybrid integration. Efficient single-photon generation was experimentally Confirmed.

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Active topological photonics

Y Ota, K Takata, T Ozawa, A Amo, Z Jia, B Kante, M Notomi, Y Arakawa, ...

Nanophotonics 9 (3), 547-567 (De Gruyter)  9 ( 3 ) 547 - 567 2020

Research paper (scientific journal), Joint Work, Accepted,  ISSN  2192-8606

　View Summary

Topological photonics has emerged as a novel route to engineer the flow of
light. Topologically-protected photonic edge modes, which are supported at the
perimeters of topologically-nontrivial insulating bulk structures, have been of
particular interest as they may enable low-loss optical waveguides immune to
structural disorder. Very recently, there is a sharp rise of interest in
introducing gain materials into such topological photonic structures, primarily
aiming at revolu-tionizing semiconductor lasers with the aid of physical
mechanisms existing in topological physics. Examples of re-markable
realizations are topological lasers with unidirectional light output under
time-reversal symmetry breaking and topologically-protected polariton and
micro/nano-cavity lasers. Moreover, the introduction of gain and loss provides
a fascinating playground to explore novel topological phases, which are in
close relevance to non-Hermitian and parity-time symmetric quantum physics and
are in general difficult to access using fermionic condensed matter systems.
Here, we review the cutting-edge research on active topological photonics, in
which optical gain plays a pivotal role. We discuss recent realizations of
topological lasers of various kinds, together with the underlying physics
explaining the emergence of topological edge modes. In such demonstrations, the
optical modes of the topological lasers are deter-mined by the dielectric
structures and support lasing oscillation with the help of optical gain. We
also address recent researches on topological photonic systems in which gain
and loss themselves essentially influence on topological prop-erties of the
bulk systems. We believe that active topological photonics provides powerful
means to advance mi-cro/nanophotonics systems for diverse applications and
topological physics itself as well.


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Fabrication and optical characterization of photonic crystal nanocavities with electrodes for gate-defined quantum dots

T Tajiri, Y Sakai, K Kuruma, SM Ji, H Kiyama, A Oiwa, J Ritzmann, ...

Japanese Journal of Applied Physics 59 (SG), SGGI05 59 ( SGGI05 ) 1 - 6 2020

Research paper (scientific journal), Joint Work, Accepted

• Access to Document (DOI)

Surface-passivated high-Q GaAs photonic crystal nanocavity with quantum dots

K Kuruma, Y Ota, M Kakuda, S Iwamoto, Y Arakawa

APL Photonics 5 (4), 046106 (AIP Publishing)  5 ( 4 ) 046106 - 046106 2020

Research paper (scientific journal), Joint Work, Accepted,  ISSN  2378-0967

　View Summary

Photonic crystal (PhC) nanocavities with high quality (Q) factors have
attracted much attention because of their strong spatial and temporal light
confinement capability. The resulting enhanced light-matter interactions are
beneficial for diverse photonic applications, ranging from on-chip optical
communications to sensing. However, currently achievable Q factors for active
PhC nanocavities, which embed active emitters inside, are much lower than those
of the passive structures because of large optical loss, presumably originating
from light scattering by structural imperfections and/or optical absorptions.
Here, we demonstrate a significant improvement of Q factors up to ~160,000 in
GaAs active PhC nanocavities using a sulfur-based surface passivation
technique. This value is the highest ever reported for any active PhC
nanocavities with semiconductor quantum dots. The surface-passivated cavities
also exhibit reduced variation in both Q factors and cavity resonant
wavelengths. We find that the improvement in the cavity performance presumably
arises from suppressed light absorption at the surface of the PhC's host
material by performing a set of PL measurements in spectral and time domains.
With the surface passivation technique, we also demonstrate a strongly-coupled
single quantum dot-cavity system based on a PhC nanocavity with a high Q factor
of ~100,000. These results will pave the way for advanced quantum dot-based
cavity quantum electrodynamics and for GaAs micro/nanophotonic applications
containing active emitters.


• Access to Document (DOI)

Strong coupling between a single quantum dot and an L4/3 photonic crystal nanocavity

K Kuruma, Y Ota, M Kakuda, S Iwamoto, Y Arakawa

Applied Physics Express 13 (8), 082009 (IOP PUBLISHING LTD)  13 ( 8 )  2020

Research paper (scientific journal), Joint Work, Accepted,  ISSN  1882-0778

　View Summary

We demonstrate strong coupling between a single quantum dot (QD) and a GaAs-based L4/3-type photonic crystal nanocavity. The L4/3 cavity supports a high theoreticalQfactor (similar to 8 x 10(6)), a small mode volume [similar to 0.32 (lambda/n)(3)], and an electric field distribution with the maximum electric field lying within the host dielectric material, which facilitates strong coupling with a QD. We fabricated L4/3 cavities and observed a highQfactor over 80 000 using photoluminescence measurement. We confirmed strong coupling between a single QD and an L4/3 cavity with aQfactor of 33 000 by observing a clear anti-crossing in the spectra.

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Slow light waveguides in topological valley photonic crystals

H Yoshimi, T Yamaguchi, Y Ota, Y Arakawa, S Iwamoto

Optics letters 45 (9), 2648-2651 (The Optical Society)  45 ( 9 ) 2648 - 2648 2020

Research paper (scientific journal), Joint Work, Accepted,  ISSN  0146-9592

• Access to Document (DOI)

Slow Light Waveguide Based on Topological Edge States in Valley Photonic Crystals

H Yoshimi, T Yamaguchi, R Katsumi, Y Ota, Y Arakawa, S Iwamoto

CLEO: Science and Innovations, STu3J. 7 (OSA)  2020-May 2020

Research paper (scientific journal), Joint Work, Accepted,  ISSN  10928081

　View Summary

We demonstrate slow light waveguides using topological valley kink states. We found in-gap high-group-index modes at bearded interfaces of silicon-based valley photonic crystals, clearing the path to build topologically-protected slow light waveguides only using semiconductors.

• Access to Document (DOI)

Microcavity-based Generation of Full Poincar\'{e} Beams with Arbitrary Skyrmion Numbers

W Lin, Y Ota, Y Arakawa, S Iwamoto

arXiv preprint arXiv:2006.15493  2020

Research paper (scientific journal), Joint Work, Accepted

In situ wavelength tuning of quantum-dot single-photon sources integrated on a CMOS-processed silicon waveguide

R Katsumi, Y Ota, A Osada, T Tajiri, T Yamaguchi, M Kakuda, S Iwamoto, ...

Applied Physics Letters 116 (4), 041103 (AIP Publishing)  116 ( 4 ) 041103 - 041103 2020

Research paper (scientific journal), Joint Work, Accepted,  ISSN  0003-6951

　View Summary

Silicon quantum photonics provides a promising pathway to realize large-scale
quantum photonic integrated circuits (QPICs) by exploiting the power of
complementary-metal-oxide-semiconductor (CMOS) technology. Toward scalable
operation of such silicon-based QPICs, a straightforward approach is to
integrate deterministic single-photon sources (SPSs). To this end, hybrid
integration of deterministic solid-state SPSs, such as those based on InAs/GaAs
quantum dots (QDs), is highly promising. However, the spectral and spatial
randomness inherent in the QDs pose a serious challenge for scalable
implementation of multiple identical SPSs on a silicon CMOS chip. To overcome
this challenge, we have been investigating a new hybrid integration technique
called transfer printing, which is based on a pick-and-place operation and
allows for the integration of desired QD SPSs on any locations on the silicon
CMOS chips at will. Nevertheless, even in this scenario, in-situ fine tuning
for perfect wavelength matching among the integrated QD SPSs will be required
for interfering photons from the dissimilar sources. Here, we demonstrate
in-situ wavelength tuning of QD SPSs integrated on a CMOS silicon chip. To
thermally tune the emission wavelengths of the integrated QDs, we augmented the
QD SPSs with optically driven heating pads. The integration of all the
necessary elements was performed using transfer printing, which largely
simplified the fabrication of the three-dimensional stack of micro/nanophotonic
structures. We further demonstrate in-situ wavelength matching between two
dissimilar QD sources integrated on the same silicon chip. Our
transfer-printing-based approach will open the possibility for realizing
large-scale QPICs that leverage CMOS technology.


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Fabrication of Monocrystalline Magneto-optical Garnet Thin Film on Insulator Substrates for Exploring Magneto-nanophotonics

S Gao, Y Ota, F Tian, Y Arakawa, S Iwamoto

JSAP Annual Meetings Extended Abstracts The 67th JSAP Spring Meeting 2020 …  2020

Joint Work

Growth-Rate-Dependent Properties of GaSb/GaAs Quantum Dots on (001) Ge Substrate by Molecular Beam Epitaxy

Zon, Phienlumlert Pakawat, Thainoi Supachok, Kiravittaya Suwit, Tandaechanurat Aniwat, Nuntawong Noppadon, Sopitpan Suwat, Yordsri Visittapong, Thanachayanont Chanchana, Kanjanachuchai Songphol, Ratanathammaphan Somchai, Panyakeow Somsak, Ota Yasutomo, Iwamoto Satoshi, Arakawa Yasuhiko

PHYSICA STATUS SOLIDI A-APPLICATIONS AND MATERIALS SCIENCE 216 ( 1 )  2019.01

Research paper (scientific journal), Joint Work, Accepted,  ISSN  1862-6300

• Access to Document (DOI)

GaAs valley photonic crystal waveguide with light-emitting InAs quantum dots

T Yamaguchi, Y Ota, R Katsumi, K Watanabe, S Ishida, A Osada, ...

Applied Physics Express 12 (6), 062005 (IOP Publishing)  12 ( 6 ) 062005 - 062005 2019

Research paper (scientific journal), Joint Work, Accepted,  ISSN  1882-0778

　View Summary

We report a valley photonic crystal (VPhC) waveguide in a GaAs slab with InAs
quantum dots (QDs) as an internal light source exploited for experimental
characterization of the waveguide. A topological interface state formed at the
interface between two topologically-distinct VPhCs is used as the waveguide
mode. We demonstrate robust propagation for near-infrared light emitted from
the QDs even under the presence of sharp bends as a consequence of the
topological protection of the guided mode. Our work will be of importance for
developing robust photonic integrated circuits with small footprints, as well
as for exploring active semiconductor topological photonics.


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Three-dimensional photonic crystal simultaneously integrating a nanocavity laser and waveguides

T Tajiri, S Takahashi, Y Ota, K Watanabe, S Iwamoto, Y Arakawa

Optica 6 (3), 296-299 6 ( 3 ) 296 - 299 2019

Research paper (scientific journal), Joint Work, Accepted

• Access to Document (DOI)

Strongly coupled single-quantum-dot–cavity system integrated on a CMOS-processed silicon photonic chip

A Osada, Y Ota, R Katsumi, M Kakuda, S Iwamoto, Y Arakawa

Physical Review Applied 11 (2), 024071 (American Physical Society (APS))  11 ( 2 )  2019

Research paper (scientific journal), Joint Work, Accepted

　View Summary

Quantum photonic integrated circuit (QPIC) is a promising tool for
constructing integrated devices for quantum technology applications. In the
optical regime, silicon photonics empowered by
complementary-metal-oxide-semiconductor (CMOS) technology provides optical
components useful for realizing large-scale QPICs. Optical nonlinearity at the
single-photon level is required for QPIC to facilitate photon-photon
interaction. However, to date, realization of optical elements with
deterministic( i.e., not probabilistic) single-photon nonlinearity by using
silicon-based components is challenging, despite the enhancement of the
functionality of QPICs based on silicon photonics. In this study, we realize
for the first time a strongly coupled InAs/GaAs quantum dot-cavity quantum
electrodynamics (QED) system on a CMOS-processed silicon photonic chip. The
heterogeneous integration of the GaAs cavity on the silicon chip is performed
by transfer printing. The cavity QED system on the CMOS photonic chip realized
in this work is a promising candidate for on-chip single-photon nonlinear
element, which constitutes the fundamental component for future applications
based on QPIC, such as, coherent manipulation and nondestructive measurement of
qubit states via a cavity, and efficient single-photon filter and router.


• Access to Document (DOI)

Spin-dependent directional emission from a quantum dot ensemble embedded in an asymmetric waveguide

W Lin, Y Ota, S Iwamoto, Y Arakawa

Optics letters 44 (15), 3749-3752 (The Optical Society)  44 ( 15 ) 3749 - 3749 2019

Research paper (scientific journal), Joint Work, Accepted,  ISSN  0146-9592

　View Summary

In this study, we examine a photonic wire waveguide embedded with an ensemble
of quantum dots that directionally emits into the waveguide depending on the
spin state of the ensemble. This is accomplished through the aid of the
spin-orbit interaction of light. The waveguide has a two-step stair-like cross
section and embeds quantum dots (QDs) only in the upper step, such that the
circular polarization of emission from the spin-polarized QDs controls the
direction of the radiation. We numerically verify that more than 70% of the
radiation from the ensemble emitter is toward a specific direction in the
waveguide. We also examine a microdisk resonator with a stair-like edge, that
supports selective coupling of the QD ensemble radiation into a whispering
galley mode rotating unidirectionally. Our study provides a foundation for
spin-dependent optoelectronic devices.


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Single plasmon generation in an InAs/GaAs quantum dot in a transfer-printed plasmonic microring resonator

A Tamada, Y Ota, K Kuruma, K Watanabe, S Iwamoto, Y Arakawa

ACS Photonics 6 (5), 1106-1110 6 ( 5 ) 1106 - 1110 2019

Research paper (scientific journal), Joint Work, Accepted,  ISSN  2330-4022

• Access to Document (DOI)

Quantum-dot single-photon source on a CMOS-processed silicon waveguide

R Katsumi, Y Ota, A Osada, T Yamaguchi, T Tajiri, M Kakuda, S Iwamoto, ...

CLEO: QELS_Fundamental Science, FM1M. 2 (IEEE)  FM1M ( 2 ) 1 - 2 2019

Research paper (scientific journal), Joint Work, Accepted,  ISSN  2160-9020

　View Summary

We report a quantum-dot single-photon source integrated onto a CMOS-processed silicon waveguide. The necessary hybrid integration was done in a simple pick-and-place manner with transfer printing, thus fully maintaining the compatibility with CMOS-back-end technology. (C) 2019 The Author(s)

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Quantum-dot single-photon source on a CMOS silicon photonic chip integrated using transfer printing

R Katsumi, Y Ota, A Osada, T Yamaguchi, T Tajiri, M Kakuda, S Iwamoto, ...

APL Photonics 4 (3), 036105 4 ( 3 )  2019

Research paper (scientific journal), Joint Work, Accepted,  ISSN  2378-0967

• Access to Document (DOI)

Photonic crystal nanocavity based on a topological corner state

Y Ota, F Liu, R Katsumi, K Watanabe, K Wakabayashi, Y Arakawa, ...

Optica 6 (6), 786-789 6 ( 6 ) 786 - 789 2019

Research paper (scientific journal), Joint Work, Accepted,  ISSN  2334-2536

　View Summary

© 2019 Optical Society of America. Topological photonics has emerged as a novel approach to engineering the flow of light and provides unprecedented means for developing diverse photonic elements, including robust optical waveguides immune to structural imperfections. However, the development of nanoscale standing-wave cavities in topological photonics is rather slow, despite its importance when building densely integrated photonic integrated circuits. In this Letter, we report a photonic crystal nanocavity based on a topological corner state, supported at a 90-deg-angled rim of a twodimensional photonic crystal. A combination of the bulk-edge and edge-corner correspondences guarantees the presence of the higher-order topological state in a hierarchical manner. We experimentally observe a corner mode that is tightly localized in space while supporting a high Q factor over 2,000, verifying its promise as a nanocavity. These results cast new light on the way to introduce nanocavities in topological photonics platforms.

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Photoluminescence properties as a function of growth mechanism for GaSb/GaAs quantum dots grown on Ge substrates

Zon, S Thainoi, S Kiravittaya, A Tandaechanurat, S Kanjanachuchai, ...

Journal of Applied Physics 126 (8), 084301 (AIP Publishing)  126 ( 8 ) 084301 - 084301 2019

Research paper (scientific journal), Joint Work, Accepted,  ISSN  0021-8979

• Access to Document (DOI)

Nanocavity based on a topological corner state in a two-dimensional photonic crystal

Y Ota, R Katsumi, K Watanabe, F Liu, K Wakabayashi, S Iwamoto, ...

CLEO: Science and Innovations, SW4J. 1 (Optics InfoBase Conference Papers)  Part F129-CLEO\_SI 2019 2019

Research paper (scientific journal), Joint Work, Accepted,  ISSN  2160-9020

　View Summary

© 2019 The Author(s) 2019 OSA. We demonstrate a photonic crystal nanocavity based on a topological corner state. The design exploits the hierarchical bulk-edge-corner correspondence for the two-dimensional photonic crystal, opening a deterministic route to introduce nanocavities in topological photonics platforms.

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Local tuning of transfer-printed quantum-dot single-photon sources on a CMOS silicon chip

R Katsumi, Y Ota, A Osada, T Tajiri, T Yamaguchi, M Kakuda, S Iwamoto, ...

2019 24th Microoptics Conference (MOC), 308-309 (IEEE)     308 - 309 2019

Research paper (scientific journal), Joint Work, Accepted

　View Summary

We report local wavelength tuning of quantum-dot single-photon sources integrated on a CMOS silicon chip as well as in-situ spectral matching between two dissimilar sources. All the necessary heterogeneous integration processes were performed in a simple pick-and-place manner based on transfer printing, largely facilitating the fabrication of complicated device structures.

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An on-chip full poincaré beam emitter based on an optical micro-ring cavity

W Lin, Y Ota, Y Arakawa, S Iwamoto

CLEO: Science and Innovations, SW4J. 4 (Optics InfoBase Conference Papers)  Part F129-CLEO\_SI 2019 2019

Research paper (scientific journal), Joint Work, Accepted

　View Summary

We numerically demonstrate an on-chip full Poincaré beam emitter. We employ a micro-ring resonator augmented with scatterer arrays, which synthesizes the Poincaré beam as a superposition of twisted beams carrying different orbital- and spin-angular momenta.

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An On-chip Full Poincare Beam Emitter Based on an Optical Micro-ring Cavity

Lin Wenbo, Ota Yasutomo, Arakawa Yasuhiko, Iwamoto Satoshi

2019 CONFERENCE ON LASERS AND ELECTRO-OPTICS (CLEO)  2019

Research paper (scientific journal), Joint Work, Accepted,  ISSN  2160-9020

In-situ wavelength tuning of quantum-dot single-photon sources integrated on a CMOS silicon chip

R Katsumi, Y Ota, A Osada, T Tajiri, T Yamaguchi, M Kakuda, S Iwamoto, ...

arXiv preprint arXiv:1909.13452  2019

Research paper (scientific journal), Joint Work, Accepted

Hybrid integration of quantum dot-nanocavity systems on silicon

Y Ota, R Katsumi, A Osada, M Kakuda, S Iwamoto, Y Arakawa

Frontiers in Optics, FM3D. 4 (Optics InfoBase Conference Papers)  Part F144-FiO 2019 2019

Research paper (scientific journal), Joint Work, Accepted

　View Summary

We discuss a transfer printing method for on-silicon hybrid integration. This technique simplifies the integration process of III-V quantum dots in nanocavities on CMOS-processed circuits, enabling single photon sources and cavity QED systems on Si.

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Growth‐Rate‐Dependent Properties of GaSb/GaAs Quantum Dots on (001) Ge Substrate by Molecular Beam Epitaxy

P Phienlumlert, S Thainoi, S Kiravittaya, A Tandaechanurat, N Nuntawong, ...

physica status solidi (a) 216 (1), 1800499  2019

Research paper (scientific journal), Joint Work, Accepted

Nanowire-quantum-dot lasers on flexible membranes

Jun Tatebayashi, Yasutomo Ota, Satomi Ishida, Masao Nishioka, Satoshi Iwamoto, Yasuhiko Arakawa

Applied Physics Express (Japan Society of Applied Physics)  11 ( 6 )  2018.06

Research paper (scientific journal), Joint Work, Accepted,  ISSN  1882-0786

　View Summary

We demonstrate lasing in a single nanowire with quantum dots as an active medium embedded on poly(dimethylsiloxane) membranes towards application in nanowire-based flexible nanophotonic devices. Nanowire laser structures with 50 quantum dots are grown on patterned GaAs(111)B substrates and then transferred from the as-grown substrates on poly(dimethylsiloxane) transparent flexible organosilicon membranes, by means of spin-casting and curing processes. We observe lasing oscillation in the transferred single nanowire cavity with quantum dots at 1.425 eV with a threshold pump pulse fluence of ∼876 μJ/cm2, which enables the realization of high-performance multifunctional NW-based flexible photonic devices.

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world's highest Q-Factor: Fabrication of a large-area 3D photonic crystal for 3D photonic circuits

Takahashi Shun, Tajiri Takeyoshi, Watanabe Katsuyuki, Ota Yasutomo, Iwamoto Satoshi, Arakawa Yasuhiko

ELECTRONICS LETTERS 54 ( 5 ) 257 - 257 2018.03

Research paper (scientific journal), Joint Work, Accepted,  ISSN  0013-5194

• Access to Document (DOI)

Circularly polarized light emission by semiconductor-based three-dimensional chiral photonic crystals

S Takahashi, Y Ota, T Tajiri, J Tatebayashi, S Iwamoto, Y Arakawa

IEICE Technical Report; IEICE Tech. Rep. 118 (349), 7-10  2018

Research paper (scientific journal), Joint Work, Accepted

Advanced Photonic Crystal Nanocavity Quantum Dot Lasers

Y Ota, K Watanabe, M Kakuda, S Iwamoto, Y Arakawa

IEICE Transactions on Electronics 101 (7), 553-560 E101C ( 7 ) 553 - 560 2018

Research paper (scientific journal), Joint Work, Accepted,  ISSN  1745-1353

• Access to Document (DOI)

High-Q nanocavities in semiconductor-based three-dimensional photonic crystals

S Takahashi, T Tajiri, K Watanabe, Y Ota, S Iwamoto, Y Arakawa

Electronics Letters 54 (5), 305-307 54 ( 5 ) 305 - 307 2018

Research paper (scientific journal), Joint Work, Accepted

　View Summary

We experimentally demonstrated high quality factors (Q-factors) of
nanocavities in three-dimensional photonic crystals by increasing the in-plane
area of the structure. Entire structures made of GaAs were fabricated by a
micro-manipulation technique, and the nanocavities contained InAs
self-assembled quantum dots that emitted near-infrared light. The obtained
Q-factor was improved to 93,000, which is 2.4-times larger than that in a
previous report of a three-dimensional photonic crystal nanocavity. Due to this
large Q-factor, we successfully observed a lasing oscillation from this cavity
mode.


• Access to Document (DOI)

Topological confinement of light in photonic crystals

S Iwamoto, Y Ota, Y Arakawa

Optics and Photonics Japan, 30aCJ1 (Optics InfoBase Conference Papers)  Part F125-OPJ 2018 2018

Research paper (scientific journal), Joint Work, Accepted

　View Summary

We will discuss a topological locarized state of light realizedin a photonic crystal (PhC) nanbeam platform. By carefuly tunig the unit cell structure, we can design two topologically distinct PhC nanobeams. The bulk-edge correpondence guarantees the existence of single localized mode at the interface between them within their common bandgap. We demonstrate the lasing osscilation using the mode as a nanocavity mode.

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Time-resolved vacuum Rabi oscillations in a quantum-dot–nanocavity system

K Kuruma, Y Ota, M Kakuda, S Iwamoto, Y Arakawa

Physical Review B 97 (23), 235448 (AMER PHYSICAL SOC)  97 ( 23 )  2018

Research paper (scientific journal), Joint Work, Accepted,  ISSN  2469-9950

　View Summary

We report time domain observation of vacuum Rabi oscillations in a single quantum dot strongly coupled to a nanocavity under incoherent optical carrier injection. We realize a photonic crystal nanocavity with a very high quality factor of >80 000 and employ it to clearly resolve the ultrafast vacuum Rabi oscillations by simple photoluminescence-based experiments. We found that the time domain vacuum Rabi oscillations were largely modified when changing the pump wavelength and intensity, even when marginal changes were detected in the corresponding photoluminescence spectra. We analyze the measured time domain oscillations by fitting to simulation curves obtained with a cavity quantum electrodynamics model. The observed modifications of the oscillation curves were mainly induced by the change in the carrier capture and dephasing dynamics in the quantum dot, as well as the change in bare-cavity emission. This result suggests that vacuum Rabi oscillations can be utilized as a highly sensitive probe for the quantum-dot dynamics. Our work points out a powerful alternative to conventional spectral-domain measurements for a deeper understanding of the vacuum Rabi dynamics in quantum-dot-based-cavity quantum electrodynamics systems.

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Scheme for media conversion between electronic spin and photonic orbital angular momentum based on photonic nanocavity

CF Fong, Y Ota, S Iwamoto, Y Arakawa

Optics express 26 (16), 21219-21234 26 ( 16 ) 21219 - 21234 2018

Research paper (scientific journal), Joint Work, Accepted,  ISSN  1094-4087

　View Summary

Light with nonzero orbital angular momentum (OAM) or twisted light is
promising for quantum communication applications such as OAM-entangled photonic
qubits. There exist photonic OAM to photonic spin angular momentum (SAM), as
well as photonic SAM to electronic SAM interfaces but not any direct photonic
OAM-electronic SAM (flying to stationary) media converter within a single
device. Here, we propose a scheme which converts photonic OAM to electronic SAM
and vice versa within a single nanophotonic device. We employed a photonic
crystal nanocavity with an embedded quantum dot (QD) which confines an electron
spin as a stationary qubit. Spin polarized emission from the QD drive the
rotation of the nanocavity modes via the strong optical spin-orbit interaction.
The rotating modes then radiate light with nonzero OAM, allowing this device to
serve as a transmitter. As this can be a unitary process, the time-reversed
case enables the device to function as a receiver. This scheme could be
generalized to other systems of resonator and quantum emitters such as a
microdisk and defects in diamond for example. Our scheme shows the potential
for realizing an (ultra)compact electronic SAM-photonic OAM interface to
accommodate OAM as an additional degree of freedom for quantum information
purposes.


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Quantum-dot nanolasers on Si photonic circuits

A Osada, Y Ota, R Katsumi, K Watanabe, S Iwamoto, Y Arakawa

2018 Conference on Lasers and Electro-Optics (CLEO), 1-2 (2018 Conference on Lasers and Electro-Optics, CLEO 2018 - Proceedings)  Part F94-CLEO\_SI 2018 2018

Research paper (scientific journal), Joint Work, Accepted

　View Summary

We report the hybrid integration of quantum dot nanolasers on silicon photonic circuits using transfer printing. The pick-and-place assembly method facilitates the integration of two nanolasers on a single CMOS-processed waveguide that supports two-wavelength output.

• Access to Document (DOI)

Quantum dot single photon sources transfer-printed on wire waveguides

R Katsumi, Y Ota, M Kakuda, S Iwamoto, Y Arakawa

CLEO: QELS_Fundamental Science, FM1H. 5 (OSA - The Optical Society)  2018 2018

Research paper (scientific journal), Joint Work, Accepted,  ISSN  2160-9020

　View Summary

We report quantum dot single photon sources coupled to glass-clad wire waveguides by transfer printing, which enables the heterogeneous source integration in a simple pick-and-place manner. A high waveguide coupling efficiency &gt
60% is experimentally demonstrated.

• Access to Document (DOI)

Nanowire–quantum-dot lasers on flexible membranes

J Tatebayashi, Y Ota, S Ishida, M Nishioka, S Iwamoto, Y Arakawa

Applied Physics Express 11 (6), 065002  2018

Research paper (scientific journal), Joint Work, Accepted

Lasing in a topological photonic crystal nanocavity

Y Ota, R Katsumi, K Watanabe, S Iwamoto, Y Arakawa

CLEO: Science and Innovations, STh3A. 4 (OSA - The Optical Society)  2018 2018

Research paper (scientific journal), Joint Work, Accepted,  ISSN  2160-9020

　View Summary

We report lasing oscillation in a zero-dimensional edge state formed at the boundary of two photonic crystal nanobeams with distinct band topologies. The topological origin of the nanocavity mode ensures a single mode operation.

• Access to Document (DOI)

Large vacuum Rabi splitting between a single quantum dot and an H0 photonic crystal nanocavity

Y Ota, D Takamiya, R Ohta, H Takagi, N Kumagai, S Iwamoto, Y Arakawa

Applied Physics Letters 112 (9), 093101 (American Institute of Physics Inc.)  112 ( 9 )  2018

Research paper (scientific journal), Joint Work, Accepted,  ISSN  0003-6951

　View Summary

Strong light matter interactions between semiconductor quantum dots and optical micro/nanocavities are useful resources for developing quantum information processing devices and for exploring diverse quantum optical phenomena. In pursuit of better device performances and novel physics, it is desirable to achieve a larger coupling constant between the quantum dot and the cavity while keeping the high coherence of the coupled system. In this letter, we report the observation of a large vacuum Rabi splitting of ∼328 μeV using a single InAs quantum dot embedded in a GaAs-based H0 photonic crystal nanocavity, which possesses a near-diffraction limited mode volume as well as a high experimental Q factor of ∼52 000. The resulting figure of merit of the strongly coupled systems, defined as a ratio of the coupling constant to the cavity decay rate, reaches 6.4, which is the record high value for semiconductor QD-nanocavity systems reported to date.

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Topological photonic crystal nanocavity laser

Y Ota, R Katsumi, K Watanabe, S Iwamoto, Y Arakawa

Communications Physics 1 (1), 1-8 (Springer Science and Business Media LLC)  1 ( 1 )  2018

Research paper (scientific journal), Joint Work, Accepted,  ISSN  2399-3650

　View Summary

Topological edge states exist at the interfaces between two
topologically-distinct materials. The presence and number of such modes are
deterministically predicted from the bulk-band topologies, known as the
bulk-edge correspondence. This principle is highly useful for predictably
controlling optical modes in resonators made of photonic crystals (PhCs),
leading to the recent demonstrations of micro-scale topological lasers.
Meanwhile, zero-dimensional topological trapped states in the nanoscale
remained unexplored, despite its importance for enhancing light-matter
interactions and for wide applications including single-mode nanolasers. Here,
we report a topological PhC nanocavity with a near-diffraction-limited mode
volume and its application to single-mode lasing. The topological origin of the
nanocavity, formed at the interface between two topologically-distinct PhCs,
guarantees the existence of only one mode within its photonic bandgap. The
observed lasing accompanies a high spontaneous emission coupling factor
stemming from the nanoscale confinement. These results encompass a way to
greatly downscale topological photonics.


• Access to Document (DOI)

world's highest Q‐Factor: Fabrication of a large‐area 3D photonic crystal for 3D photonic circuits

anonymous

Electronics Letters 54 (5), 257-257  2018

Research paper (scientific journal), Joint Work, Accepted

Two dimensional photonic crystal nanocavities with InAs/GaAs quantum dot active regions embedded by MBE regrowth

QH Vo, Y Ota, K Watanabe, T Kageyama, S Iwamoto, Y Arakawa

Japanese Journal of Applied Physics 57 (8S2), 08PD03 57 ( 8 )  2018

Research paper (scientific journal), Joint Work, Accepted,  ISSN  0021-4922

• Access to Document (DOI)

Transfer-printed single-photon sources coupled to wire waveguides

R Katsumi, Y Ota, M Kakuda, S Iwamoto, Y Arakawa

Optica 5 (6), 691-694 (The Optical Society)  5 ( 6 ) 691 - 691 2018

Research paper (scientific journal), Joint Work, Accepted,  ISSN  2334-2536

　View Summary

Photonic integrated circuits (PICs) are attractive platforms to perform
large-scale quantum information processing. While highly-functional PICs (e.g.
silicon based photonic-circuits) and high-performance single photon sources
(SPSs, e.g. compound-semiconductor quantum dots (QDs)) have been independently
demonstrated, their combination for single-photon-based applications has still
been limited. This is largely due to the complexities of introducing SPSs into
existing PIC platforms, which are generally realized with different materials
and using distinct fabrication protocols. Here, we report a novel approach to
combine SPSs and PICs prepared independently. We employ transfer printing, by
which multiple desired SPSs can be integrated in a simple pick-and-place manner
with a theoretical waveguide coupling efficiency >99%, fulfilling the demanding
requirements of large-scale quantum applications. Experimentally, we
demonstrated QD-based SPSs with high waveguide coupling efficiencies, together
with the integration of two SPSs into a waveguide. Our approach will accelerate
scalable fusion between modern PICs and cutting-edge quantum technologies.


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Transfer-printed quantum-dot nanolasers on a silicon photonic circuit

A Osada, Y Ota, R Katsumi, K Watanabe, S Iwamoto, Y Arakawa

Applied Physics Express 11 (7), 072002 (Japan Society of Applied Physics)  11 ( 7 )  2018

Research paper (scientific journal), Joint Work, Accepted,  ISSN  1882-0786

　View Summary

Quantum-dot (QD) nanolasers integrated on a silicon photonic circuit are demonstrated for the first time. QD nanolasers based on one-dimensional photonic crystal nanocavities containing InAs/GaAs QDs are integrated on CMOS-processed silicon waveguides with silicon dioxide cladding. We employed transfer printing, whereby the three-dimensional stack of photonic nanostructures is assembled in a pick-and-place manner. The lasing operation and waveguide coupling of an assembled single nanolaser are confirmed through micro-photoluminescence spectroscopy. Furthermore, by repetitive transfer printing, two QD nanolasers integrated onto a single silicon waveguide are demonstrated, opening a path to the development of compact light sources potentially applicable to wavelength division multiplexing.

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IEICE Technical Report

ST KIT, Y Ota, T Tajiri, J Tatebayashi, S Iwamoto, Y Arakawa, ...

Workshop Date 118 (128)  2018

Joint Work

Control of angular momentum of photons by photonic nanostructures

S Iwamoto, Y Ota, CF Fong, Y Arakawa

JSAP Annual Meetings Extended Abstracts The 65th JSAP Spring Meeting 2018, 47-47  2018

Joint Work

Single photon emission and lasing oscillation in a plasmonic microring resonator containing self-assembled quantum dots

A Tamada, Y Ota, K Kuruma, K Watanabe, S Iwamoto, Y Arakawa

IEICE Technical Report; IEICE Tech. Rep. 117 (407), 269-274  2018

Joint Work

Scheme for Optical Orbital-to-Electronic Spin Angular Momentum Media Conversion using a Photonic Crystal Nanocavity

CF Fong, Y Ota, S Iwamoto, Y Arakawa

JSAP Annual Meetings Extended Abstracts The 65th JSAP Spring Meeting 2018 …  2018

Joint Work

High‐Q nanocavities in semiconductor‐based three‐dimensional photonic crystals

S Takahashi, T Tajiri, K Watanabe, Y Ota, S Iwamoto, Y Arakawa

Electronics Letters 54 (5), 305-307  2018

Joint Work

Control of circularly polarized light emission by semiconductor-based three-dimensional chiral photonic crystals

S Takahashi, Y Ota, T Tajiri, J Tatebayashi, S Iwamoto, Y Arakawa

IEICE Technical Report; IEICE Tech. Rep. 117 (407), 1-4  2018

Joint Work

Method for generating a photonic NOON state with quantum dots in coupled nanocavities (vol 96, 013853, 2017)

Kenji Kamide, Yasutomo Ota, Satoshi Iwamoto, Yasuhiko Arakawa

PHYSICAL REVIEW A (AMER PHYSICAL SOC)  96 ( 2 )  2017.08

Research paper (scientific journal), Joint Work, Accepted,  ISSN  2469-9926

• Access to Document (DOI)

Enhanced optical Stark shifts in a single quantum dot embedded in an H1 photonic crystal nanocavity

H Takagi, Y Ota, N Kumagai, S Ishida, S Iwamoto, Y Arakawa

Applied Physics Express 10 (6), 062002 (IOP PUBLISHING LTD)  10 ( 6 )  2017

Research paper (scientific journal), Joint Work, Accepted,  ISSN  1882-0778

　View Summary

We demonstrate large optical Stark shifts in a single quantum dot embedded in a modified H1 photonic crystal nanocavity. We designed the nanocavity to simultaneously possess a high Q factor, a small mode volume, and a high coupling efficiency to the external laser field. This nanocavity enabled the observation of a large Stark shift of 70 mu eV even under very weak laser irradiation. The large shift was sustained by only four intracavity photons on average, paving the way for the development of ultralow-power quantum/classical optical devices. (C) 2017 The Japan Society of Applied Physics

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Demonstration of lasing oscillation in a plasmonic microring resonator containing quantum dots fabricated by transfer printing

A Tamada, Y Ota, K Kuruma, J Ho, K Watanabe, S Iwamoto, Y Arakawa

Japanese Journal of Applied Physics 56 (10), 102001 (Japan Society of Applied Physics)  56 ( 10 )  2017

Research paper (scientific journal), Joint Work, Accepted,  ISSN  1347-4065

　View Summary

We demonstrate room-temperature lasing oscillation in a plasmonic microring resonator containing InAs/GaAs self-assembled quantum dots. The resonator is composed of a GaAs microring placed on an atomically flat silver surface. Such a structure was fabricated by transfer printing, through which we can pick the dielectric microring and place it on the silver surface at will, hence maintaining a high-quality metal surface without introducing any complex fabrication process. Our result will be important in the development of nanoscale light sources in future densely integrated plasmonic circuits.

• Access to Document (DOI)

Control of circularly polarized light electromagnetic field using chiral photonic crystals--Artificial optical activity and control of QD emission

S Iwamoto, S Takahashi, T Tajiri, Y Ota, Y Arakawa

IEICE Technical Report; IEICE Tech. Rep. 116 (389), 1-3  2017

Research paper (scientific journal), Joint Work, Accepted

Circularly polarized vacuum field in three-dimensional chiral photonic crystals probed by quantum dot emission

S Takahashi, Y Ota, T Tajiri, J Tatebayashi, S Iwamoto, Y Arakawa

Physical Review B 96 (19), 195404 (AMER PHYSICAL SOC)  96 ( 19 )  2017

Research paper (scientific journal), Joint Work, Accepted,  ISSN  2469-9950

　View Summary

The modification of a circularly polarized vacuum field in three-dimensional chiral photonic crystals was measured by spontaneous emission from quantum dots in the structures. Due to the circularly polarized eigenmodes along the helical axis in the GaAs-based mirror-asymmetric structures we studied, we observed highly circularly polarized emission from the quantum dots. Both spectroscopic and time-resolved measurements confirmed that the obtained circularly polarized light was influenced by a large difference in the photonic density of states between the orthogonal components of the circular polarization in the vacuum field.

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A photonic crystal nanocavity with a quantum dot active region embedded by MBE regrowth

QH Vo, Y Ota, K Watanabe, T Kageyama, S Iwamoto, Y Arakawa

2017 22nd Microoptics Conference (MOC), 90-91 (Institute of Electrical and Electronics Engineers Inc.)  2017-   90 - 91 2017

Research paper (scientific journal), Joint Work, Accepted

　View Summary

We fabricated a two dimensional photonic crystal nanocavity embedding a spatially-isolated active region containing InAs quantum dots using crystal regrowth with molecular beam epitaxy. We observed a cavity mode with a quality factor over 10,000, despite the existence of a mound structure on top of the buried active region due to faceting during the regrowth.

• Access to Document (DOI)

Growth of InGaAs/GaAs nanowire-quantum dots on AlGaAs/GaAs distributed Bragg reflectors for laser applications

J Tatebayashi, S Kako, J Ho, Y Ota, S Iwamoto, Y Arakawa

Journal of Crystal Growth 468, 144-148  2017

Research paper (scientific journal), Joint Work, Accepted

Time-domain observation of vacuum rabi oscillations in a strongly coupled quantum dot-nanocavity system

K Kuruma, Y Ota, M Kakuda, S Iwamoto, Y Arakawa

CLEO: QELS_Fundamental Science, JTh1E. 4 (OSA - The Optical Society)  2017   1 - 2 2017

Research paper (scientific journal), Joint Work, Accepted,  ISSN  2160-9020

　View Summary

We report the time-domain observation of vacuum Rabi oscillations in a single quantum dot-photonic crystal nanocavity system under optical carrier injection. A significantlyimproved cavity Q-factor facilitates the direct access to the ultrafast exciton-photon dynamics.

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Thresholdless quantum dot nanolaser

Y Ota, M Kakuda, K Watanabe, S Iwamoto, Y Arakawa

Optics express 25 (17), 19981-19994 (OPTICAL SOC AMER)  25 ( 17 ) 19981 - 19994 2017

Research paper (scientific journal), Joint Work, Accepted,  ISSN  1094-4087

　View Summary

Thresholdless lasing is an outstanding challenge in laser science and is achievable only in devices having near unity quantum efficiency even when not lasing. Such lasers are expected to exhibit featureless linear light output curves. However, such thresholdless behavior hinders identification of the laser transition, triggering a long-lasting argument on how to identify the lasing. Here, we demonstrate thresholdless lasing in a semiconductor quantum dot nanolaser with a photonic crystal nanocavity. We employ cavity resonant excitation for enabling the thresholdless operation via focused carrier injection into high cavity field regions. Under conventional (above bandgap) excitation, the same nanolaser exhibits a typical thresholded lasing transition, thereby facilitating a systematic comparison between the thresholdless and thresholded laser transitions in the single device. Our approach enables a clear verification of the thresholdless lasing and reveals core elements for its realization using quantum dots, paving the way to the development of ultimately energyefficient nanolasers. (C) 2017 Optical Society of America

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Thresholdless lasing with quantum dot gain

Y Ota, D Takamiya, K Watanabe, M Kakuda, S Iwamoto, Y Arakawa

CLEO: Science and Innovations, STh4N. 3 (OSA - The Optical Society)  2017   1 - 2 2017

Research paper (scientific journal), Joint Work, Accepted,  ISSN  2160-9020

　View Summary

We demonstrate thresholdless lasing with quantum dot gain, operated under cavity resonant excitation. The lasing behavior is systematically compared with that under conventional above bandgap excitation, providing a firm verification of the thresholdless operation.

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Publisher's Note: Method for generating a photonic NOON state with quantum dots in coupled nanocavities [Phys. Rev. A 96, 013853 (2017)]

K Kamide, Y Ota, S Iwamoto, Y Arakawa

Physical Review A 96 (2), 029901  2017

Research paper (scientific journal), Joint Work, Accepted

Optical coupling between atomically thin black phosphorus and a two dimensional photonic crystal nanocavity

Y Ota, R Moriya, N Yabuki, M Arai, M Kakuda, S Iwamoto, T Machida, ...

Applied Physics Letters 110 (22), 223105 (AMER INST PHYSICS)  110 ( 22 )  2017

Research paper (scientific journal), Joint Work, Accepted,  ISSN  0003-6951

　View Summary

Atomically thin black phosphorus (BP) is an emerging two dimensional (2D) material exhibiting bright photoluminescence in the near infrared region. Coupling its radiation to photonic nanostructures will be an important step toward the realization of 2D material based nanophotonic devices that operate efficiently in the near infrared region, which includes the technologically important optical telecommunication wavelength bands. In this letter, we demonstrate the optical coupling between atomically thin BP and a 2D photonic crystal nanocavity. We employed a home-build dry transfer apparatus for placing a thin BP flake on the surface of the nanocavity. Their optical coupling was analyzed through measuring cavity mode emission under optical carrier injection at room temperature. Published by AIP Publishing.

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Method for generating a photonic NOON state with quantum dots in coupled nanocavities

K Kamide, Y Ota, S Iwamoto, Y Arakawa

Physical Review A 96 (1), 013853 (AMER PHYSICAL SOC)  96 ( 1 )  2017

Research paper (scientific journal), Joint Work, Accepted,  ISSN  2469-9926

　View Summary

We propose a method to generate path-entangled NOON-state photons from quantum dots and coupled nanocavities. In the systems we considered, cavity mode frequencies are tuned close to the biexciton two-photon resonance. Under appropriate conditions, the system can have the target NOON state in the energy eigenstate, as a consequence of destructive quantum interference. The NOON state can be generated by a resonant laser excitation. This method, first introduced for a two-photon NOON state (N = 2), can be extended toward a higher NOON state (N > 2) based on our recipe, which is applied to the case of N = 4 as an example.

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Manipulation of dynamic nuclear spin polarization in single quantum dots by photonic environment engineering

CF Fong, Y Ota, S Iwamoto, Y Arakawa

Physical Review B 95 (24), 245423  2017

Research paper (scientific journal), Joint Work, Accepted

Guiding of laser light from a nanocavity in a three-dimensional photonic crystal

T Tajiri, S Takahashi, Y Ota, K Watanabe, S Iwamoto, Y Arakawa

2017 Conference on Lasers and Electro-Optics (CLEO), 1-2 (OSA - The Optical Society)  2017   1 - 2 2017

Research paper (scientific journal), Joint Work, Accepted,  ISSN  2160-9020

　View Summary

A nanocavity laser and two orthogonal waveguides are integrated in a threedimensional photonic crystal. Guiding of the laser light from the nanocavity through the waveguides is demonstrated experimentally.

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プラズモニックマイクロリング共振器に埋め込まれた量子ドットにおける Purcell 効果の観測

A Tamada, Y Ota, K Kuruma, J Ho, K Watanabe, S Iwamoto, Y Arakawa

応用物理学会学術講演会講演予稿集 第 64 回応用物理学会春季学術講演会, 1029-1029  2017

Research paper (scientific journal), Joint Work, Accepted

単一自己形成量子ドットにおける光検出電子スピン共鳴の解析

A Ulhaq, MS Skolnick, Y Ota, S Iwamoto, Y Arakawa

 2017

Research paper (scientific journal), Joint Work, Accepted

励起スピン依存一方向レーザ発振が可能な光共振器の設計

W Lin, Y Ota, S Iwamoto, Y Arakawa

応用物理学会学術講演会講演予稿集 第 78 回応用物理学会秋季学術講演会, 845-845  2017

Research paper (scientific journal), Joint Work, Accepted

プラズモニック微小リング共振器中に埋め込まれた自己形成量子ドットからの単一光子発生

A Tamada, Y Ota, K Kuruma, J Ho, K Watanabe, S Iwamoto, Y Arakawa

応用物理学会学術講演会講演予稿集 第 78 回応用物理学会秋季学術講演会, 886-886  2017

Research paper (scientific journal), Joint Work, Accepted

Analysis on Optically-detected Electron Spin Resonance in Single Self-Assembled Quantum Dots

CF Fong, E Chekhovich, A Ulhaq, M Skolnick, Y Ota, S Iwamoto, ...

JSAP Annual Meetings Extended Abstracts The 64th JSAP Spring Meeting 2017 …  2017

Joint Work

量子光回路応用に向けた量子ドットのオンチップ光励起の検討

長田有登， 勝見亮太， 角田雅弘， 太田泰友， 岩本敏， 荒川泰彦

応用物理学会学術講演会講演予稿集 第 78 回応用物理学会秋季学術講演会, 863-863 78th 2017

Joint Work

Photoluminescence Properties of GaSb/GaAs Quantum Dots Grown on Ge and GaAs Substrates

Z Zon, S Thainoi, S Kiravittaya, A Tandaechanurat, S Panyakeow, Y Ota, ...

JSAP Annual Meetings Extended Abstracts The 64th JSAP Spring Meeting 2017 …  2017

Joint Work

High-Q Two-dimensional Photonic Crystal Nanocavity on Glass with an Upper

R Kawata, A Fujita, N Pholsen, S Iwamoto, Y Ota

Opt. Express 25, 19981  2017

Joint Work

Control of Circularly Polarized Electromagnetic Field using Chiral Photonic Crystals-Artificial Optical Activity and Control of QD Emission

S Iwamoto, S Takahashi, T Tajiri, Y Ota, Y Arakawa

電子情報通信学会技術研究報告 116 (388 (OPE2016 116-158)), 1-3  2017

Joint Work

Effect of metal side claddings on emission decay rates of single quantum dots embedded in a sub-wavelength semiconductor waveguide

T Yamamoto, Y Ota, S Ishida, N Kumagai, S Iwamoto, Y Arakawa

Japanese Journal of Applied Physics 55 (8S3), 08RC02 (IOP PUBLISHING LTD)  55 ( 8 )  2016

Research paper (scientific journal), Joint Work, Accepted,  ISSN  0021-4922

　View Summary

We experimentally investigate the emission decay rates of self-assembled single InAs quantum dots (QDs) embedded in sub-wavelength semiconductor waveguides with and without metal side claddings. Compared with as-grown single QDs, we observe a clear suppression (enhancement) in the radiative decay rates of single InAs QDs embedded in the sub-wavelength semiconductor waveguides without (with) metal cladding, respectively. The decay rate for QDs in metal-clad waveguides is similar to 2 times faster than that in waveguides without metal. Numerical calculations using models that include the effects of structural imperfections show good agreement with the experimental results, and reveal that the most important structural imperfection is the gap between the metal and the semiconductor. (C) 2016 The Japan Society of Applied Physics.

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Demonstration of a plasmonic laser using quantum dot gain medium

J Ho, J Tatebayashi, S Sergent, CF Fong, Y Ota, S Iwamoto, Y Arakawa

2016 Compound Semiconductor Week (CSW)[Includes 28th International … (IEEE)   2016

Research paper (scientific journal), Joint Work, Accepted

Control of quantum dot light emission by chiral photonic crystal structures

S Iwamoto, S Takahashi, T Tajiri, Y Ota, Y Arakawa

2016 Progress in Electromagnetic Research Symposium (PIERS), 2572-2572 (IEEE)     2572 - 2572 2016

Research paper (scientific journal), Joint Work, Accepted

Control of Light Polarization using Photonic and Phononic Crystals

S Iwamoto, S Takahashi, I Kim, T Tajiri, Y Ota, Y Arakawa

Asia Communications and Photonics Conference, AS2F. 2 (Asia Communications and Photonics Conference, ACP)  2016-November 2016

Research paper (scientific journal), Joint Work, Accepted,  ISSN  2162-108X

　View Summary

Photonic and phnonic crystals offer the possibilities of controlling light polarization efficiently. Here, we discuss giant optical rotation in a chiral photonic crystal and enhanced photoelastic modulation in a phononic crystal cavity.

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Advanced nanoscale light sources based on photonic crystal nanocavity quantum dot lasers

Y Ota, S Iwamoto, Y Arakawa

IEICE Technical Report; IEICE Tech. Rep. 116 (372), 9-13 (電子情報通信学会)  116 ( 372 ) 9 - 13 2016

Research paper (scientific journal), Joint Work, Accepted,  ISSN  0913-5685

A nanowire-based plasmonic quantum dot laser

J Ho, J Tatebayashi, S Sergent, CF Fong, Y Ota, S Iwamoto, Y Arakawa

Nano letters 16 (4), 2845-2850 (AMER CHEMICAL SOC)  16 ( 4 ) 2845 - 2850 2016

Research paper (scientific journal), Joint Work, Accepted,  ISSN  1530-6984

　View Summary

Quantum dots enable strong carrier confinement and exhibit a delta-function like density of states, offering significant improvements to laser performance and high temperature stability when used as a gain medium. However, quantum dot lasers have been limited to photonic cavities that are diffraction-limited and further miniaturization to meet the demands of nanophotonic-electronic integration applications is challenging based on existing designs. Here we introduce the first quantum dot-based plasmonic laser to reduce the cross-sectional area of nanowire quantum dot lasers below the cutoff limit of photonic modes while maintaining the length in the order of the lasing wavelength. Metal organic chemical vapor deposition grown GaAs-AlGaAs core-shell nanowires containing InGaAs quantum dot stacks are placed directly on a silver film, and lasing was observed from single nanowires originating from the InGaAs quantum dot emission into the low-loss higher order plasmonic mode. Lasing threshold pump fluences as low as similar to 120 mu J/cm(2) was observed at 7 K, and lasing was observed up to 125 K. Temperature stability from the quantum dot gain, leading to a high characteristic temperature was demonstrated. These results indicate that high-performance, miniaturized quantum dot lasers can be realized with plasmonics.

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p-shell carrier assisted dynamic nuclear spin polarization in single quantum dots at zero external magnetic field

CF Fong, Y Ota, E Harbord, S Iwamoto, Y Arakawa

Physical Review B 93 (12), 125306  2016

Research paper (scientific journal), Joint Work, Accepted

Position dependent optical coupling between single quantum dots and photonic crystal nanocavities

K Kuruma, Y Ota, M Kakuda, D Takamiya, S Iwamoto, Y Arakawa

Applied Physics Letters 109 (7), 071110 (AMER INST PHYSICS)  109 ( 7 )  2016

Research paper (scientific journal), Joint Work, Accepted,  ISSN  0003-6951

　View Summary

We demonstrate precise and quick detection of the positions of quantum dots (QDs) embedded in two-dimensional photonic crystal nanocavities. We apply this technique to investigate the QD position dependence of the optical coupling between the QD and the nanocavity. We use a scanning electron microscope (SEM) operating at a low acceleration voltage to detect surface bumps induced by the QDs buried underneath. This enables QD detection with a sub-10 nm precision. We then experimentally measure the vacuum Rabi spectra to extract the optical coupling strengths (gs) between single QDs and cavities, and compare them to the values estimated by a combination of the SEM-measured QD positions and electromagnetic cavity field simulations. We found a highly linear relationship between the local cavity field intensities and the QD-cavity gs, suggesting the validity of the point dipole approximation used in the estimation of the gs. The estimation using SEM has a small standard deviation of 66.2%, which potentially enables the high accuracy prediction of g prior to optical measurements. Our technique will play a key role for deeply understanding the interaction between QDs and photonic nanostructures and for advancing QD-based cavity quantum electrodynamics. Published by AIP Publishing.

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Modulation of Dynamic Nuclear Spin Polarization in Single InAs/GaAs Quantum Dots by Photonic Bandgap Effect

CF Fong, Y Ota, S Iwamoto, Y Arakawa

JSAP Annual Meetings Extended Abstracts, 3086-3086  2016

Joint Work

Demonstration of a three-dimensional photonic crystal nanocavity in a <110>-layered diamond structure

T. Tajiri, S. Takahashi, Y. Ota, J. Tatebayashi, S. Iwamoto, Y. Arakawa

Applied Physics Letters 107 ( 071102 )  2015.08

Research paper (scientific journal), Joint Work, Accepted

• Access to Document (DOI)

Effect of metal side claddings on emission decay rate of single quantum dots embedded in a subwavelength semiconductor waveguide

Takumi Yamamoto, Yasutomo Ota, Satomi Ishida, Naoto Kumagai, Satoshi Iwamoto, Yasuhiko Arakawa

2015 20TH MICROOPTICS CONFERENCE (MOC) (IEEE)   2015

Research paper (scientific journal), Joint Work, Accepted

　View Summary

We measured the emission decay rates of self-assembled InAs single quantum dots (QDs) embedded in subwavelength-width semiconductor waveguides with and without Au side claddings. The Au claddings increased the decay rate of single QDs by similar to 2 times, which is consistent with numerical simulations taking account of fabrication imperfection.

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Demonstration of a three-dimensional photonic crystal nanocavity in a⟨ 110⟩-layered diamond structure

T Tajiri, S Takahashi, Y Ota, J Tatebayashi, S Iwamoto, Y Arakawa

Applied Physics Letters 107 (7), 071102  2015

Research paper (scientific journal), Joint Work, Accepted

Circularly polarized light emission of quantum dots at the band edge of three-dimensional chiral photonic crystals

S Takahashi, T Tajiri, Y Ota, J Tatebayashi, S Iwamoto, Y Arakawa

CLEO: QELS_Fundamental Science, FF1C. 2 (IEEE)  2015-August   1551p 2015

Research paper (scientific journal), Joint Work, Accepted,  ISSN  2160-9020

　View Summary

We demonstrate highly circularly polarized emission from quantum dots in semiconductor chiral photonic crystals. The emission is influenced by the difference in density of states between the orthogonal circular polarizations at the polarization band edge.

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Asymmetric out-of-plane power distribution in a two-dimensional photonic crystal nanocavity

Y Ota, S Iwamoto, Y Arakawa

Optics letters 40 (14), 3372-3375 (OPTICAL SOC AMER)  40 ( 14 ) 3372 - 3375 2015

Research paper (scientific journal), Joint Work, Accepted,  ISSN  0146-9592

　View Summary

Conventional air-bridge two-dimensional photonic crystal (2D-PhC) nanocavities emit light with an equal power distribution for upward and downward out-of-plane directions. Some applications, however, require concentration of the radiation in a preferred direction. In this Letter, we design a 2D-PhC nanocavity that radiates dominantly into one of the out-of-plane directions with a narrow far-field distribution. Our design is based on a conventional air-bridge L3 photonic crystal nanocavity. The asymmetric out-of-plane power distribution is achieved solely by adding periodic shallow holes on the slab surface, which also function as a second-order grating for the directional beaming. (C) 2015 Optical Society of America

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Influence of the relative positions of quantum dots and nanocavities on the optical coupling strength

K Kuruma, Y Ota, D Takamiya, M Kakuda, S Iwamoto, Y Arakawa

2015 11th Conference on Lasers and Electro-Optics Pacific Rim (CLEO-PR) 3, 1-2 (Institute of Electrical and Electronics Engineers Inc.)  3 2015

Research paper (scientific journal), Joint Work, Accepted

　View Summary

We use scanning electron microscopy to precisely measure the locations of quantum dots buried in photonic crystal nanocavities. We show that well-positioned dots (at the field maximum) can exhibit vacuum Rabi splittings larger than 180μeV.

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Single emitter vacuum Rabi splitting measured through direct free space spontaneous emission

Y Ota, R Ohta, N Kumagai, S Iwamoto, Y Arakawa

2015 Conference on Lasers and Electro-Optics (CLEO), 1-2 (IEEE)  2015-August   1551p 2015

Research paper (scientific journal), Joint Work, Accepted,  ISSN  2160-9020

　View Summary

We measured the vacuum Rabi splitting of a single quantum emitter through direct free space spontaneous emission. This lays the groundwork for accessing diverse cavity quantum electrodynamics phenomena manifesting themselves only in the spontaneous emission.

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Self-frequency conversion nanocavity lasers

Y Ota, K Watanabe, S Iwamoto, Y Arakawa

IEICE Technical Report; IEICE Tech. Rep. 115 (46), 13-17  2015

Research paper (scientific journal), Joint Work, Accepted

Room-temperature lasing in GaAs nanowires embedding multi-stacked InGaAs/GaAs quantum dots

J Tatebayashi, S Kako, J Ho, Y Ota, S Iwamoto, Y Arakawa

CLEO: Science and Innovations, SM2F. 1 (IEEE)  2015-August   2267 2015

Research paper (scientific journal), Joint Work, Accepted,  ISSN  2160-9020

　View Summary

We report the demonstration of room-temperature lasing in a single GaAs nanowire embedding 50-stacked In0.22Ga0.78As/GaAs quantum dots at a lasing emission energy of 1.37 eV with a threshold pump pulse fluence of 138 mu j/cm(2). (C) 2015 Optical Society of America

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Room-temperature lasing in a single nanowire with quantum dots

J Tatebayashi, S Kako, J Ho, Y Ota, S Iwamoto, Y Arakawa

Nature Photonics 9 (8), 501-505 (NATURE PUBLISHING GROUP)  9 ( 8 ) 501 - + 2015

Research paper (scientific journal), Joint Work, Accepted,  ISSN  1749-4885

　View Summary

Semiconductor nanowire lasers are promising as ultrasmall, highly efficient coherent light emitters in the fields of nano-photonics, nano-optics and nanobiotechnology(1,2). Although there have been several demonstrations of nanowire lasers using homogeneous bulk gainmaterials(3-14) or multi-quantum-wells/disks(15-17), it is crucial to incorporate lower-dimensional quantum nano-structures into the nanowire to achieve superior device performance in relation to threshold current, differential gain, modulation bandwidth and temperature sensitivity. The quantum dot is a useful and essential that can meet these requirements(18). However, difficulties in forming stacks of quantum dots in a single nanowire hamper the realization of lasing operation. Here, we demonstrate room-temperature lasing of a single nanowire containing 50 quantum dots by properly designing the nanowire cavity and tailoring the emission energy of each dot to enhance the optical gain. Our demonstration paves the way toward ultrasmall lasers with extremely low power consumption for integrated photonic systems.

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Vacuum Rabi spectra of a single quantum emitter

Y Ota, R Ohta, N Kumagai, S Iwamoto, Y Arakawa

Physical review letters 114 (14), 143603 (AMER PHYSICAL SOC)  114 ( 14 ) 143603 - 143603 2015

Research paper (scientific journal), Joint Work, Accepted,  ISSN  0031-9007

　View Summary

We report the observation of the vacuum Rabi splitting of a single quantum emitter by measuring its direct spontaneous emission into free space. We use a semiconductor quantum dot inside a photonic crystal nanocavity, in conjunction with an appropriate cavity design and filtering with a polarizer and an aperture, enabling the extraction of the inherently weak emitter's signal. The emitter's vacuum Rabi spectra exhibit clear differences from those measured by detecting the cavity photon leakage. Moreover, we observe an asymmetric vacuum Rabi spectrum induced by interference between the emitter and cavity detection channels. Our observations lay the groundwork for accessing various cavity quantum electrodynamics phenomena that manifest themselves only in the emitter's direct spontaneous emission.

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Dynamic Nuclear Spin Polarization in the Presence of Multiple Excitonic Complexes in Single InAs/GaAs Quantum Dots at Zero Applied Magnetic Field

CF Fong, Y Ota, E Harbord, S Iwamoto, Y Arakawa

JSAP Annual Meetings Extended Abstracts The 62nd JSAP Spring Meeting 2015 …  2015

Joint Work

Theoretical analysis of nanolaser with a few quantum dot gain

V ELFVING, Y OTA, K KAMIDE, S IWAMOTO, Y ARAKAWA

JSAP Annual Meetings Extended Abstracts The 62nd JSAP Spring Meeting 2015 …  2015

Joint Work

Measuring the second-order coherence of a nanolaser by intracavity frequency doubling

Yasutomo Ota, Katsuyuki Watanabe, Satoshi Iwamoto, Yasuhiko Arakawa

Physical Review A - Atomic, Molecular, and Optical Physics 89 ( 2 )  2014.02

Research paper (scientific journal), Joint Work, Accepted,  ISSN  1050-2947

　View Summary

We measured the second-order coherence at zero time delay, g(2)(0), of a high-Q photonic crystal nanocavity quantum dot laser below and above the lasing threshold, via detecting visible emission originated from the second harmonic generation (SHG) occurring within the laser cavity. The efficiency of the nonlinear frequency conversion process, defined by SHG intensity divided by the square of laser output intensity, is shown to be proportional to g(2)(0), and hence is used for the measurement. The obtained g(2)(0) values show good agreement with those measured by a Hanbury Brown-Twiss interferometer equipped with ultrafast superconducting single-photon detectors. © 2014 American Physical Society.

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Measuring the second-order coherence of a nanolaser by intracavity frequency doubling

Ota Yasutomo, Watanabe Katsuyuki, Iwamoto Satoshi, Arakawa Yasuhiko

PHYSICAL REVIEW A 89 ( 2 )  2014.02

Research paper (scientific journal), Joint Work, Accepted,  ISSN  1050-2947

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Measuring the second-order coherence of a nanolaser by intracavity frequency doubling

Yasutomo Ota, Katsuyuki Watanabe, Satoshi Iwamoto, Yasuhiko Arakawa

PHYSICAL REVIEW A (AMER PHYSICAL SOC)  89 ( 2 )  2014.02

Research paper (scientific journal), Joint Work, Accepted,  ISSN  2469-9926

　View Summary

We measured the second-order coherence at zero time delay, g((2))(0), of a high-Q photonic crystal nanocavity quantum dot laser below and above the lasing threshold, via detecting visible emission originated from the second harmonic generation (SHG) occurring within the laser cavity. The efficiency of the nonlinear frequency conversion process, defined by SHG intensity divided by the square of laser output intensity, is shown to be proportional to g((2))(0), and hence is used for the measurement. The obtained g((2))(0) values show good agreement with those measured by a Hanbury Brown-Twiss interferometer equipped with ultrafast superconducting single-photon detectors.

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Circular dichroism in a three-dimensional semiconductor chiral photonic crystal

S Takahashi, T Tajiri, Y Ota, J Tatebayashi, S Iwamoto, Y Arakawa

Applied Physics Letters 105 (5), 051107 105 ( 051107 )  2014

Research paper (scientific journal), Joint Work, Accepted

• Access to Document (DOI)

Cavity quantum electrodynamics in quantum dot-photonic crystal nanocavity coupled system with large g/κ

S Iwamoto, Y Ota, H Takagi, D Takamiya, Y Arakawa

CLEO: Science and Innovations, SM3M. 4  2014

Research paper (scientific journal), Joint Work, Accepted

Cavity Quantum Electrodynamics in Quantum Dot-Photonic Crystal Nanocavity Coupled System with Large g/kappa

Satoshi Iwamoto, Yasutomo Ota, Hiroyuki Takagi, Daisaku Takamiya, Yasuhiko Arakawa

2014 CONFERENCE ON LASERS AND ELECTRO-OPTICS (CLEO) (IEEE)   2014

Research paper (scientific journal), Joint Work, Accepted,  ISSN  2160-9020

　View Summary

We report experimental progresses in cavity quantum electrodynamics using H1 and H0-type photonic crystal nanoacvities embedding single quantum dots. Strong coupling and enhanced optical Stark effect in these systems with large g/kappa will be discussed.

Cavity QED in Quantum Dot-photonic Crystal Nanocavity Coupled Systems

Y Arakawa, S Iwamoto, Y Ota, K Kamide

Laser Science, LTu4H. 1 (Optics InfoBase Conference Papers)   2014

Research paper (scientific journal), Joint Work, Accepted

• Access to Document (DOI)

Frequency-doubled photonic crystal nanocavity lasers

Y Ota, K Watanabe, S Iwamoto, Y Arakawa

SPIE Newsroom  2014

Research paper (scientific journal), Joint Work, Accepted

Measuring the second-order coherence of a nanolaser by intracavity frequency doubling

Y Ota, K Watanabe, S Iwamoto, Y Arakawa

Physical Review A 89 (2), 023824  2014

Research paper (scientific journal), Joint Work, Accepted

Measurement of the second order coherence of a nanolaser through its intra-cavity second harmonic generation

Y Ota, K Watanabe, S Iwamoto, Y Arakawa

CLEO: Science and Innovations, SW1G. 2 (IEEE)  2014-January 2014

Research paper (scientific journal), Joint Work, Accepted,  ISSN  2160-9020

　View Summary

We measured the second order coherence of a photonic crystal nanolaser through measuring frequency doubling occurring within the laser nanocavity. This method enables investigation of the intensity noise properties even far below the lasing threshold.

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Highly uniform, multi-stacked InGaAs/GaAs quantum dots embedded in a GaAs nanowire

J Tatebayashi, Y Ota, S Ishida, M Nishioka, S Iwamoto, Y Arakawa

Applied Physics Letters 105 (10), 103104 (AMER INST PHYSICS)  105 ( 10 )  2014

Research paper (scientific journal), Joint Work, Accepted,  ISSN  0003-6951

　View Summary

We demonstrate a highly uniform, dense stack of In0.22Ga0.78As/GaAs quantum dot (QD) structures in a single GaAs nanowire (NW). The size (and hence emission energy) of individual QD is tuned by careful control of the growth conditions based on a diffusion model of morphological evolution of NWs and optical characterization. By carefully tailoring the emission energies of individual QD, dot-to-dot inhomogeneous broadening of QD stacks in a single NW can be as narrow as 9.3 meV. This method provides huge advantages over traditional QD stack using a strain-induced Stranski-Krastanow growth scheme. We show that it is possible to fabricate up to 200 uniform QDs in single GaAs NWs using this growth technique without degradation of the photoluminescence intensity. (C) 2014 AIP Publishing LLC.

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Cavity quantum electrodynamics in quantum dot-photonic crystal nanocavity coupled system with large G/k

Iwamoto S., Ota Y., Takagi H., Takamiya D., Arakawa Y.

Conference on Lasers and Electro-Optics Europe - Technical Digest (Conference on Lasers and Electro-Optics Europe - Technical Digest)  2014-January 2014

Joint Work

　View Summary

We report experimental progresses in cavity quantum electrodynamics using H1 and H0-type photonic crystal nanoacvities embedding single quantum dots. Strong coupling and enhanced optical Stark effect in these systems with large g/kwill be discussed.

Measurement of Nuclear Spin Build-up Time in Single InAs/GaAs Quantum Dots by Modulated Circularly Polarized Excitation

CF Fong, Y Ota, E Harbord, S Iwamoto, Y Arakawa

JSAP Annual Meetings Extended Abstracts The 75th JSAP Autumn Meeting 2014 …  2014

Joint Work

Cavity quantum electrodynamics in quantum dot-photonic crystal nanocavity coupled system with large g/KΚ

Iwamoto S., Ota Y., Takagi H., Takamiya D., Arakawa Y.

Optics InfoBase Conference Papers (Optics InfoBase Conference Papers)   2014

Joint Work

　View Summary

We report experimental progresses in cavity quantum electrodynamics using H1 and H0-type photonic crystal nanoacvities embedding single quantum dots. Strong coupling and enhanced optical Stark effect in these systems with large g/KΚ will be discussed. © 2014 OSA.

Growth of high-quality InAs quantum dots embedded in GaAs nanowire structures on Si substrates

Jinkwan Kwoen, Katsuyuki Watanabe, Yasutomo Ota, Satoshi Iwamoto, Yasuhiko Arakawa

Physica Status Solidi (C) Current Topics in Solid State Physics 10 ( 11 ) 1496 - 1499 2013.11

Research paper (scientific journal), Joint Work, Accepted,  ISSN  1862-6351

　View Summary

We present the growth of InAs quantum dots (QD) embedded in GaAs nanowires (NW) on silicon and demonstrate clear single photon emission. Sharp excitonic emission (linewidth of 162 μeV) and the generation of single photons (g(2)(0) = 0.18) was observed by low temperature photoluminescence measurements, suggesting a high optical quality which can be attributed to the high crystal quality of the QD structure. It is believed that the crystal quality is high due to the Stranski-Krastanov (S-K) mode of the growth. This structure may open new ways for the integration of such photon emitters into future 'on-silicon' quantum optical circuits. © 2013 WILEY-VCH Verlag GmbH &amp
Co. KGaA, Weinheim.

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Electro-mechanical Q factor control of photonic crystal nanobeam cavity

R Ohta, Y Ota, H Takagi, N Kumagai, K Tanabe, S Ishida, S Iwamoto, ...

Japanese Journal of Applied Physics 52 (4S), 04CG01 52 ( 4 )  2013

Research paper (scientific journal), Joint Work, Accepted,  ISSN  0021-4922

　View Summary

We design and demonstrate a photonic crystal nanobeam cavity with a Q factor controllable by a micro-electro-mechanical system (MEMS). The cavity is evanescently coupled to an adjacent nanobeam waveguide, and its Q factor is controlled by electro-mechanically adjusting the gap distance between them. We experimentally demonstrate control of the Q factor from 2,250 to 2,750, by applying voltage from 0 to 11 V. © 2013 The Japan Society of Applied Physics.

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Enhancement of valence band mixing in individual InAs/GaAs quantum dots by rapid thermal annealing

E Harbord, Y Ota, Y Igarashi, M Shirane, N Kumagai, S Ohkouchi, ...

Japanese Journal of Applied Physics 52 (12R), 125001 (IOP PUBLISHING LTD)  52 ( 12 )  2013

Research paper (scientific journal), Joint Work, Accepted,  ISSN  0021-4922

　View Summary

We measure polarization resolved photoluminescence from excitonic complexes in tens of single InAs/GaAs quantum dots (QDs) over a wide range of energies in two samples: one as-grown, the other subjected to rapid thermal annealing (RTA). thing the linear polarization of the X+ emission as a probe of the valence band mixing (VBM), we find that RTA enhances QD VBM, attributed to the increase in QD height. We complement our measurements with 8-band k . p calculations, which suggest the increase in height on annealing is responsible for this enhancement. (C) 2013 The Japan Society of Applied Physics

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Self-frequency summing in quantum dot photonic crystal nanocavity lasers

Y Ota, K Watanabe, S Iwamoto, Y Arakawa

Applied Physics Letters 103 (24), 243115 103 ( 24 )  2013

Research paper (scientific journal), Joint Work, Accepted,  ISSN  0003-6951

• Access to Document (DOI)

Self-frequency summing in photonic crystal nanocavity quantum dot lasers

Yasutomo Ota, Katsuyuki Watanabe, Satoshi Iwamoto, Yasuhiko Arakawa

Pacific Rim Conference on Lasers and Electro-Optics, CLEO - Technical Digest 103 ( 24 )  2013

Research paper (scientific journal), Joint Work, Accepted,  ISSN  0003-6951

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Self-frequency summing processes in photonic crystal nanocavity quantum dot lasers are observed. High quality factors and small mode volumes of the nanocavities facilitate efficient nonlinear frequency summing processes, generating a variety of visible emission lines. © 2013 IEEE.

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Self-frequency Summing in Photonic Crystal Nanocavity Quantum Dot Lasers

Yasutomo Ota, Katsuyuki Watanabe, Satoshi Iwamoto, Yasuhiko Arakawa

2013 CONFERENCE ON LASERS AND ELECTRO-OPTICS PACIFIC RIM (CLEO-PR) (IEEE)   2013

Research paper (scientific journal), Joint Work, Accepted

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Self-frequency summing processes in photonic crystal nanocavity quantum dot lasers are observed. High quality factors and small mode volumes of the nanocavities facilitate efficient nonlinear frequency summing processes, generating a variety of visible emission lines.

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Self-frequency Summing in Photonic Crystal Nanocavity Quantum Dot Lasers

Ota Yasutomo, Watanabe Katsuyuki, Iwamoto Satoshi, Arakawa Yasuhiko

2013 CONFERENCE ON LASERS AND ELECTRO-OPTICS PACIFIC RIM (CLEO-PR)  2013

Research paper (scientific journal), Joint Work, Accepted

Self-frequency summing in photonic crystal nanocavity quantum dot lasers

Y Ota, K Watanabe, S Iwamoto, Y Arakawa

Conference on Lasers and Electro-Optics/Pacific Rim, MI2_7  2013

Research paper (scientific journal), Joint Work, Accepted

Observation of enhanced exciton decay rate of single InAs quantum dots in nanoscale metal-semi conductor-metal plasmonic structures

T Yamamoto, Y Ota, E Harbord, S Ishida, N Kumagai, S Iwamoto, ...

2013 International Conference on Solid State Devices and Materials, 1020-1021  2013

Research paper (scientific journal), Joint Work, Accepted

Nonlinear photonics in single quantum dot-photonic crystal nanocavity couples systems

S Iwamoto, Y Ota, H Takagi, N Kumagai, Y Arakawa

Conference on Lasers and Electro-Optics/Pacific Rim, MI2_1 (IEEE)   2013

Research paper (scientific journal), Joint Work, Accepted

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We will present our recent advances on single quantum dot-photonic crystal nanocavity coupled systems. Cavity enhanced two-photon emission and large optical Stark effect with extremely low control power in these systems will be mainly discussed.

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Nanocavity-based self-frequency conversion laser

Y Ota, K Watanabe, S Iwamoto, Y Arakawa

Optics Express 21 (17), 19778-19789 (OPTICAL SOC AMER)  21 ( 17 ) 19778 - 19789 2013

Research paper (scientific journal), Joint Work, Accepted,  ISSN  1094-4087

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Self-frequency conversion (SFC), where both laser oscillation and nonlinear frequency conversion occurs in the same laser crystal, has been used to efficiently extend the operational wavelength of lasers. Downsizing of the cavity mode volume (V) and increasing the quality factor (Q) could lead to a more efficient conversion process, mediated by enhanced n-th order nonlinearities that generally scale as (Q/V)(n). Here, we demonstrate nanocavity-based SFC by utilizing photonic crystal nanocavity quantum dot lasers. The high Q and small V supported in semiconductor-based nanocavities facilitate efficient SFC to generate visible light, even with only a few photons present in the laser cavity. The combined broadband quantum dot gain and small device footprint enables the monolithic integration of 26 different-color nanolasers (spanning 493-627 nm) within a micro-scale region. These nanolasers provide a new platform for studying few-photon nonlinear optics, and for realizing full-color lasers on a single semiconductor chip. (C) 2013 Optical Society of America

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Multi-color visible light generation by self-frequency doubling in photonic crystal nanocavity quantum dot lasers

Y Ota, K Watanabe, S Iwamoto, Y Arakawa

CLEO: Science and Innovations, CTh3F. 2 (IEEE)   2013

Research paper (scientific journal), Joint Work, Accepted,  ISSN  2160-9020

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We report multi-color visible light generation from photonic crystal nanocavity lasers exhibiting broadband quantum dot gain in the near infrared. The visible emission is produced though self-frequency doubling, which efficiently occurs within the high Q nanocavities.

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Large vacuum rabi splitting in an H0 photonic crystal nanocavity-quantum dot system

D Takamiya, Y Ota, R Ohta, H Takagi, N Kumagai, S Ishida, S Iwamoto, ...

Conference on Lasers and Electro-Optics/Pacific Rim, MI2_2 (Pacific Rim Conference on Lasers and Electro-Optics, CLEO - Technical Digest)   2013

Research paper (scientific journal), Joint Work, Accepted

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We demonstrate a large vacuum Rabi splitting in an H0 photonic crystal nanocavity-quantum dot system. The nanocavity with an ultra-small mode volume enabled us to observe the largest splitting ever reported using single InAsquantum dots. © 2013 IEEE.

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Growth of high‐quality InAs quantum dots embedded in GaAs nanowire structures on Si substrates

J Kwoen, K Watanabe, Y Ota, S Iwamoto, Y Arakawa

physica status solidi (c) 10 (11), 1496-1499  2013

Research paper (scientific journal), Joint Work, Accepted

Giant optical rotation in a three-dimensional semiconductor chiral photonic crystal

S Takahashi, A Tandaechanurat, R Igusa, Y Ota, J Tatebayashi, ...

Optics express 21 (24), 29905-29913 (Optical Society of American (OSA))  21 ( 24 ) 29905 - 29913 2013

Research paper (scientific journal), Joint Work, Accepted,  ISSN  1094-4087

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Optical rotation is experimentally demonstrated in a semiconductor-based three-dimensional chiral photonic crystal (PhC) at a telecommunication wavelength. We design a rotationally-stacked woodpile PhC structure, where neighboring layers are rotated by 45° and four layers construct a single helical unit. The mirror-asymmetric PhC made from GaAs with sub-micron periodicity is fabricated by a micro-manipulation technique. The linearly polarized light incident on the structure undergoes optical rotation during transmission. The obtained results show good agreement with numerical simulations. The measurement demonstrates the largest optical rotation angle as large as ~ 23° at 1.3 μm wavelength for a single helical unit. © 2013 Optical Society of America.

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Formation and optical properties of multi-stack InGaAs quantum dots embedded in GaAs nanowires by selective metalorganic chemical vapor deposition

J Tatebayashi, Y Ota, S Ishida, M Nishioka, S Iwamoto, Y Arakawa

Journal of crystal growth 370, 299-302  2013

Research paper (scientific journal), Joint Work, Accepted

Wide range Q-factor control in a photonic crystal nanobeam cavity incorporating quantum dots

R Ohta, Y Ota, N Kumagai, S Ishida, S Iwamoto, Y Arakawa

CLEO: Science and Innovations, CM4F. 4 (IEEE)   2013

Research paper (scientific journal), Joint Work, Accepted,  ISSN  2160-9020

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We develop a Q-factor controllable photonic crystal nanobeam cavity incorporating quantum dots. Wide Q-factor control from 3,500 to 14,000 is demonstrated by means of MEMS, supplying bias from 0 to 18 V.

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Rabi Oscillations of a Single InAs Quantum Dot Assisted by a Photonic Crystal Nanobeam Cavity.

A Enderlin, Y Ota, S Iwamoto, Y Arakawa

JSAP Annual Meetings Extended Abstracts The 60th JSAP Spring Meeting 2013 …  2013

Joint Work

High guided mode-cavity mode coupling for an efficient extraction of spontaneous emission of a single quantum dot embedded in a photonic crystal nanobeam cavity

Alexandre Enderlin, Yasutomo Ota, Ryuichi Ohta, Naoto Kumagai, Satomi Ishida, Satoshi Iwamoto, Yasuhiko Arakawa

PHYSICAL REVIEW B (AMER PHYSICAL SOC)  86 ( 7 )  2012.08

Research paper (scientific journal), Joint Work, Accepted,  ISSN  1098-0121

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We demonstrate efficient extraction of a single InAs quantum dot spontaneous emission through an air-suspended waveguide to which a photonic crystal nanobeam cavity is coupled. First, the quantum dot emission into the cavity mode is enhanced due to a high Purcell effect arising from a large quality factor and a small mode volume of the cavity mode. Second, the cavity photons can be efficiently transferred to the guided mode by optimizing the design of a structure that exhibits a high coupling rate between the two modes. This configuration has lead to the observation of a high extraction efficiency (79%) of the quantum dot emission through the waveguide. Moreover, as a result of the high extraction efficiency to the guided mode, the unwanted microphotoluminescence coupling to the free space modes and detected from the top surface of the sample is strongly suppressed. Indeed, we show that it exhibits a negative peak as a function of the detuning between the cavity mode energy and the quantum dot transition energy.

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Cavity quantum electrodynamics and lasing oscillation in single quantum dot-photonic crystal nanocavity coupled systems

Y Arakawa, S Iwamoto, M Nomura, A Tandaechanurat, Y Ota

IEEE Journal of Selected Topics in Quantum Electronics 18 (6), 1818-1829 (IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC)  18 ( 6 ) 1818 - 1829 2012

Research paper (scientific journal), Joint Work, Accepted,  ISSN  1077-260X

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Our recent advances in solid-state cavity quantum electrodynamics and lasing oscillation in single quantum dot (QD)-photonic crystal (PhC) nanocavity coupled systems are discussed. These include the fabrication of high-quality 2-D PhC nanocavities (Q &gt; 50 000), which enabled the generation of spontaneous two-photon emission from a single QD, and the realization of lasing oscillation with single QD gain in the strong coupling regime. Moreover, we have fabricated high-quality 3-D PhC nanocavities (Q similar to 38 500), which have facilitated the realization of both lasing oscillation and the Purcell effect. Lasing oscillation in a 1-D PhC nanobeam cavity with gain produced by a few QDs has also been demonstrated.

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Electro-mechanical control of Q factor in photonic crystal nanobeam cavity

R Ohta, Y Ota, H Takagi, N Kumagai, K Tanabe, S Ishida, S Iwamoto, ...

SSDM 2013  2012

Research paper (scientific journal), Joint Work, Accepted

Formation of a single In (Ga) As/GaAs quantum dot embedded in a site-controlled GaAs nanowire by metalorganic chemical vapor deposition for application to single photon sources

J Tatebayashi, Y Ota, D Karunathillake, S Ishida, M Nishioka, S Iwamoto, ...

MRS Online Proceedings Library 1439 (1), 115-119 (Materials Research Society Symposium Proceedings)  1439   115 - 119 2012

Research paper (scientific journal), Joint Work, Accepted,  ISSN  0272-9172

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We report the formation and optical properties of site-controlled InAs/GaAs quantum dots (QDs) embedded in GaAs nanowires (NWs) by selective metalorganic chemical vapor deposition for application to single photon sources. InAs/GaAs QD-in-NWs with various InAs thicknesses are realized on patterned GaAs(111)B substrates in the form of InAs/GaAs heterostructures and identified by structural analyses using scanning transmission electron microscopy and photoluminescence characterization. Sharp excitonic emission peaks at 10 K from single QD-in-NWs with the narrowest exciton linewidth of 87 μe V are observed. Light emission from the single QD-in-NW shows photon antibunching which evidences single photon emission from high-quality QD-in-NWs. © 2012 Materials Research Society.

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Site-controlled formation of InAs/GaAs quantum-dot-in-nanowires for single photon emitters

J Tatebayashi, Y Ota, S Ishida, M Nishioka, S Iwamoto, Y Arakawa

Applied Physics Letters 100 (26), 263101 (AMER INST PHYSICS)  100 ( 26 )  2012

Research paper (scientific journal), Joint Work, Accepted,  ISSN  0003-6951

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We report the demonstration of site-controlled InAs/GaAs quantum dots (QDs) embedded in GaAs nanowires (NWs) by selective metalorganic chemical vapor deposition. InAs/GaAs quantum-dot-innanowires (QD-in-NWs) with various InAs thicknesses are realized on patterned GaAs(111) B substrates in the form of InAs/GaAs heterostructures and identified by structural analyses using scanning transmission electron microscopy and photoluminescence characterization. Sharp excitonic emission peaks at 10K from single QD-in-NWs with the narrowest exciton linewidth of 87 mu eV are observed. Light emission from the single QD-in-NW shows photon antibunching, along with biexciton-exciton cascaded emission process, which evidences single photon emission from high-quality QD-in-NWs. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4731208]

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Optical properties of site-controlled InGaAs quantum dots embedded in GaAs nanowires by selective metalorganic chemical vapor deposition

J Tatebayashi, Y Ota, S Ishida, M Nishioka, S Iwamoto, Y Arakawa

Japanese Journal of Applied Physics 51 (11S), 11PE13 (JAPAN SOC APPLIED PHYSICS)  51 ( 11 )  2012

Research paper (scientific journal), Joint Work, Accepted,  ISSN  0021-4922

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We report the optical properties of site-controlled InGaAs quantum dots (QDs) embedded in GaAs nanowires (NWs) grown by selective metalorganic chemical vapor deposition (MOCVD). InGaAs/GaAs QD-in-NWs with various QD heights and In compositions are realized on patterned GaAs(111) B substrates in the form of InGaAs/GaAs heterostructures, and identified by structural analyses using scanning transmission electron microscopy, photoluminescence (PL) characterization, and numerical analyses of the band structure using a single-band effective mass approximation. Room temperature (RT) light emission is observed at 1.03 mu m from InGaAs/GaAs QD-in-NWs which is indicative of the formation of high-quality InGaAs QD-in-NWs. Sharp emission peaks from exciton and biexciton of single In(Ga) As QD-in-NWs are observed by using mu-PL characterization at 10 K. (C) 2012 The Japan Society of Applied Physics

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Nanocavity-enhanced optical Stark shift in a single quantum dot under extremely low excitation power

H Takagi, Y Ota, N Kumagai, S Ishida, S Iwamoto, Y Arakawa

2012 Conference on Lasers and Electro-Optics (CLEO), 1-2 (IEEE)   2012

Research paper (scientific journal), Joint Work, Accepted,  ISSN  2160-9020

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An enhanced optical Stark shift in a single quantum dot is demonstrated using a newly-designed H1-type photonic crystal nanocavity. A 70 mu eV shift is observed at 450nW; 110-times lower than excitation powers reported in the literature.

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Intra-cavity frequency doubling in photonic crystal nanocavity quantum dot lasers

Y Ota, K Watanabe, S Iwamoto, Y Arakawa

IEEE Photonics Conference 2012, 610-611 (IEEE)     610 - 611 2012

Research paper (scientific journal), Joint Work, Accepted,  ISSN  2374-0140

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We report visible light generation via intra-cavity frequency doubling in photonic crystal nanocavity quantum dot lasers. A strong field enhancement in the nanocavity enables the efficient conversion process, even with only a few intra-cavity photons.

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High Q H1 photonic crystal nanocavities with efficient vertical emission

H Takagi, Y Ota, N Kumagai, S Ishida, S Iwamoto, Y Arakawa

Optics express 20 (27), 28292-28300 (OPTICAL SOC AMER)  20 ( 27 ) 28292 - 28300 2012

Research paper (scientific journal), Joint Work, Accepted,  ISSN  1094-4087

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We report on newly-designed H1-type photonic crystal (PhC) nanocavities that simultaneously exhibit high Q factors, small mode volumes, and high external coupling efficiencies (eta perpendicular to) of light radiated above the PhC membrane. Dipole modes of the H1 PhC nanocavities, which are doubly-degenerate and orthogonally-polarized in theory, are investigated both by numerical calculations and experiments. Through modifying the sizes and positions of the air-holes near to the defect cavity, a Q factor of 62,000 is achieved, accompanied with an improved eta perpendicular to of 0.38 (assuming an objective lens with a numerical aperture of 0.65). A further increase of.. to more than 0.60 is observed at the expense of slight degradation of Q factor (down to 50,000). We further experimentally confirm the increase of both Q and eta perpendicular to, using micro-photoluminescence measurements, and demonstrate high Q factors up to 25,000: the highest value ever reported for dipole modes in H1 PhC nanocavities. (C) 2012 Optical Society of America

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High guided mode–cavity mode coupling for an efficient extraction of spontaneous emission of a single quantum dot embedded in a photonic crystal nanobeam cavity

A Enderlin, Y Ota, R Ohta, N Kumagai, S Ishida, S Iwamoto, Y Arakawa

Physical Review B 86 (7), 075314  2012

Research paper (scientific journal), Joint Work, Accepted

Wavelength Tunable Quantum Dot Single-Photon Source with a Side Gate

T Nakaoka, Y Tamura, T Miyazawa, K Watanabe, Y Ota, S Iwamoto, ...

Japanese Journal of Applied Physics 51 (2S), 02BJ05 (JAPAN SOC APPLIED PHYSICS)  51 ( 2 )  2012

Research paper (scientific journal), Joint Work, Accepted,  ISSN  0021-4922

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We demonstrate photon antibunching from a wavelength controlled quantum dot single-photon source with a side gate. The photoluminescence peaks from the quantum dots embedded in the side-gate structure are clearly identified as a neutral exciton and a neutral biexciton by the studies of excitation-power dependence, polarization dependence, and photon correlation. The neutral exciton energy is controlled by the side gate via the quantum confined Stark effect. Measurement of the second-order autocorrelation function indicates g((2))(0) = 0.07 at 0 V, 0.14 at 0.8 V, and 0.24 at 0.9 V. The results show g((2))(0)s are below the 0.5 limit necessary for classification as a single photon source even under applied gate voltage. We also show a biexciton-exciton cascade which can be used to create entangled photon pairs. (C) 2012 The Japan Society of Applied Physics

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Effects of growth temperature of partial GaAs cap on InAs quantum dots in In‐flush process for single dot spectroscopy

N Kumagai, S Ohkouchi, M Shirane, Y Igarashi, M Nomura, Y Ota, ...

physica status solidi c 8 (2), 248-250  2011

Research paper (scientific journal), Joint Work, Accepted

Effects of growth temperature of partial GaAs cap on InAs quantum dots in In-flush process for single dot spectroscopy

Naoto Kumagai, Shunsuke Ohkouchi, Masayuki Shirane, Yuichi Igarashi, Masahiro Nomura, Yasutomo Ota, Shinichi Yorozu, Satoshi Iwamoto, Yasuhiko Arakawa

PHYSICA STATUS SOLIDI C: CURRENT TOPICS IN SOLID STATE PHYSICS, VOL 8, NO 2 (WILEY-V C H VERLAG GMBH)  8 ( 2 )  2011

Research paper (scientific journal), Joint Work, Accepted,  ISSN  1862-6351

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We have investigated effects of growth temperature of partial GaAs cap (T-cap) on InAs quantum dots (QDs) in indium-flush (In-flush) process with atomic force microscopy (AFM) and micro photoluminescence (mu-PL) measurements. T-cap in In-flush process are varied from 385 degrees C to 485 degrees C as an experimental parameter. In order to investigate the effects of T-cap on structural property of single InAs QD, shape of QD in initial capping process are characterized by AFM measurements in air at room temperature. While isotropic shape of QDs is kept in low T-cap conditions below about 440 degrees C, in-plane anisotropy of initial shape of QDs are increased with increasing of T-cap due to elongation to the [1 (1) over bar 0] direction. mu-PL measurements are performed at 7K for the investigation of the effects of T-cap on optical property in single InAs QDs. In low T-cap conditions from 410 degrees C to 435 degrees C, distinct emissions from excitonic states in single QDs are observed. In the same T-cap range, the AFM result shows that isotropic shape of QDs is kept. On the other hand, in high T-cap conditions above about 440 degrees C, indefinite peaks and broad emissions appear remarkably. Excitonic emissions which are observed in low T-cap range are hardly observed in this high T-cap range. (C) 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

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Competing influence of an in-plane electric field on the Stark shifts in a semiconductor quantum dot

T Nakaoka, Y Tamura, T Saito, T Miyazawa, K Watanabe, Y Ota, ...

Applied Physics Letters 99 (18), 181109 99 ( 18 )  2011

Research paper (scientific journal), Joint Work, Accepted,  ISSN  0003-6951

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We report on the fabrication of a side-gate structure which enables a purely lateral electric field to be applied onto a self-assembled quantum dot. The lateral field produces an unconventional M'-shaped exciton energy shift-a blueshift followed by a redshift. The unconventional energy shift is reproduced by calculation. The calculation shows that only the positively charged exciton shows the unconventional shift. The origin is attributed to the field-induced hole-concentration in the bottom-corner of the dot, which strongly enhances the repulsive direct Coulomb interaction and reduces the exciton binding energy. © 2011 American Institute of Physics.

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New method to isolate and distribute photoluminescence emissions from InAs quantum dots over a wide-wavelength range

S Ohkouchi, N Kumagai, M Shirane, Y Igarashi, M Nomura, Y Ota, ...

Journal of crystal growth 323 (1), 250-253 (ELSEVIER SCIENCE BV)  323 ( 1 ) 250 - 253 2011

Research paper (scientific journal), Joint Work, Accepted,  ISSN  0022-0248

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We propose a new method to isolate and distribute the photoluminescence emission wavelengths of InAs quantum dots (QDs) over a wide-wavelength range by the growth of the partial GaAs capping layer at low temperature and annealing processes. When the partial capping layer was grown at 485 degrees C, the emission wavelengths of the QDs were distributed within a small range around the mean wavelength. On the other hand, when the partial capping layer was grown at a lower temperature of 423 degrees C, the emission wavelengths of the individual QDs were isolated and distributed over a wide range. Thus fabricated QDs are effective for the QD based devices such as single photon sources. (C) 2010 Elsevier B.V. All rights reserved.

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Strong coupling between a photonic crystal nanobeam cavity and a single quantum dot

R Ohta, Y Ota, M Nomura, N Kumagai, S Ishida, S Iwamoto, Y Arakawa

Applied Physics Letters 98 (17), 173104 (AMER INST PHYSICS)  98 ( 17 )  2011

Research paper (scientific journal), Joint Work, Accepted,  ISSN  0003-6951

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We demonstrated the strong coupling between a one-dimensional photonic crystal nanobeam cavity and a single quantum dot (QD). Thanks to a high quality factor (similar to 25 000) with small mode volume [0.38 X (n/lambda)(3)] of the nanobeam cavity, an anticrossing behavior with a vacuum Rabi splitting of 226 mu eV was observed. The ratio of the QD-cavity coupling strength to the cavity decay rate, which is a figure of merit of quantum optical applications, is estimated to 2.1. This is the highest value among any QD-based cavity quantum electrodynamics systems reported so far. (C) 2011 American Institute of Physics. [doi: 10.1063/1.3579535]

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Spontaneous two-photon emission from a single quantum dot

Y Ota, S Iwamoto, N Kumagai, Y Arakawa

Physical review letters 107 (23), 233602 (AMER PHYSICAL SOC)  107 ( 23 ) 233602 - 233602 2011

Research paper (scientific journal), Joint Work, Accepted,  ISSN  0031-9007

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Spontaneous two-photon emission from a solid-state single quantum emitter is observed. We investigated photoluminescence from the neutral biexciton in a single semiconductor quantum dot coupled with a high Q photonic crystal nanocavity. When the cavity is resonant to the half energy of the biexciton, the strong vacuum field in the cavity inspires the biexciton to simultaneously emit two photons into the mode, resulting in clear emission enhancement of the mode. Meanwhile, the suppression of other single photon emission from the biexciton was observed, as the two-photon emission process becomes faster than the others at the resonance.

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Observation of Purcell effect in a 3D photonic crystal nanocavity with a single quantum dot

A Tandaechanurat, Y Ota, N Kumagai, S Ishida, S Iwamoto, Y Arakawa

International Quantum Electronics Conference, J967 (Optics InfoBase Conference Papers)     10 - 11 2011

Research paper (scientific journal), Joint Work, Accepted

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We observed the Purcell effect in a three-dimensional photonic crystal nanocavity with a single quantum dot. The enhancement and suppression factors of the spontaneous emission rate are ∼2 and 1.6, respectively. © 2011 IEEE.

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Charged and neutral biexciton-exciton cascade in a single quantum dot within a photonic bandgap

M. Shirane, Y. Igarashi, Y. Ota, M. Nomura, N. Kumagai, S. Ohkouchi, A. Kirihara, S. Ishida, S. Iwamoto, S. Yorozu, Y. Arakawa

PHYSICA E-LOW-DIMENSIONAL SYSTEMS & NANOSTRUCTURES (ELSEVIER SCIENCE BV)  42 ( 10 ) 2563 - 2566 2010.09

Research paper (scientific journal), Joint Work, Accepted,  ISSN  1386-9477

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We investigate the recombination dynamics of positively charged and neutral biexcitons and excitons in a single InAs/GaAs quantum dot (QD) within a two-dimensional (2D) photonic bandgap (PBG). The 20 PBG makes the exciton lifetime four times longer and enhances photon-extraction efficiency compared to those without the PBG. Photon cross-correlation measurements demonstrate the cascade emissions of both charged and neutral biexcitons-excitons from the same QD. In the charged case, a hole in the p-shell relaxes into the s-shell between the cascade, and the corresponding transition is confirmed based on the spin configuration. The long exciton lifetime with the PBG helps us to reveal the spin dynamics that did not clearly appear in intrinsic QDs. (C) 2010 Elsevier B.V. All rights reserved.

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Charged and neutral biexciton–exciton cascade in a single quantum dot within a photonic bandgap

M Shirane, Y Igarashi, Y Ota, M Nomura, N Kumagai, S Ohkouchi, ...

Physica E: Low-dimensional Systems and Nanostructures 42 (10), 2563-2566  2010

Research paper (scientific journal), Joint Work, Accepted

Laser oscillation in a strongly coupled single-quantum-dot–nanocavity system

M Nomura, N Kumagai, S Iwamoto, Y Ota, Y Arakawa

Nature Physics 6 (4), 279-283 (Springer Science and Business Media LLC)  6 ( 4 ) 279 - 283 2010

Research paper (scientific journal), Joint Work, Accepted,  ISSN  1745-2473

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Suppression of indefinite peaks in InAs/GaAs quantum dot spectrum by low temperature capping in the indium-flush method

N Kumagai, S Ohkouchi, S Nakagawa, M Nomura, Y Ota, M Shirane, ...

Physica E: Low-dimensional Systems and Nanostructures 42 (10), 2753-2756 (ELSEVIER SCIENCE BV)  42 ( 10 ) 2753 - 2756 2010

Research paper (scientific journal), Joint Work, Accepted,  ISSN  1386-9477

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We have investigated effects of growth temperature of thin GaAs capping layer in the initial stage of indium-flush process using atomic force microscopy and microscopic photoluminescence (mu-PL) methods. The shape of capped InAs quantum dot (QD) and its mu-PL properties are sensitive to the growth temperature of thin GaAs capping layer. In the case of the high temperature cap, the QD shape in initial capping stage is elongated along the [1 1 -0] direction, and mu-PL spectrum shows several peaks accompanied with indefinite peaks. On the other hand, the low temperature case, the QD shape is kept in isotropic and mu-PL spectrum shows distinctive emissions from excitonic states of the QD with suppressed indefinite peaks. These results indicate that the low temperature capping is effective to keep an isotropic shape of QD and suppress indefinite peaks. (C) 2009 Elsevier B.V. All rights reserved.

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Spin dynamics of excited trion states in a single InAs quantum dot

Y Igarashi, M Shirane, Y Ota, M Nomura, N Kumagai, S Ohkouchi, ...

Physical Review B 81 (24), 245304  2010

Research paper (scientific journal), Joint Work, Accepted

Phonon-induced asymmetry in vacuum Rabi doublet for coupled quantum dot-cavity system

Y Ota, N Kumagai, S Ohkouchi, M Shirane, M Nomura, S Ishida, ...

Quantum Electronics and Laser Science Conference, QThM2 (IEEE)   2010

Research paper (scientific journal), Joint Work, Accepted

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We experimentally observed theoretically-predicted, phonon-induced asymmetry in vacuum Rabi doublet spectra for a coupled quantum dot-cavity system in the resonance. Asymmetry is also observed in the intensity of the off-resonant cavity mode emissions. (C) 2010 Optical Society of America

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Observation of unique photon statistics of single artificial atom laser

M Nomura, N Kumagai, S Iwamoto, Y Ota, Y Arakawa

Physica E: Low-dimensional Systems and Nanostructures 42 (10), 2489-2492 (ELSEVIER SCIENCE BV)  42 ( 10 ) 2489 - 2492 2010

Research paper (scientific journal), Joint Work, Accepted,  ISSN  1386-9477

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We demonstrate a photonic crystal nanocavity laser essentially driven by a self-assembled InAs/GaAs single quantum dot gain and its unique photon statistics. Gain tuning measurements and photon correlation measurements indicated that a single quantum dot plays a substantial role in the laser oscillation. Photon correlation measurements showed a distinct transition from anti-bunching to Poissonian via photon bunching around the threshold with the increase of the excitation power. Numerical simulations, including contributions of other light sources besides a single quantum dot, indicated that the photon bunching feature around the threshold can be enhanced by the interfusion of incoherent photons into the cavity mode. (C) 2009 Elsevier B.V. All rights reserved.

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Neutralization of positively charged excitonic state in single InAs quantum dot by Si delta doping

N Kumagai, S Ohkouchi, M Shirane, Y Igarashi, M Nomura, Y Ota, ...

Journal of Physics: Conference Series 245 (1), 012088 (Institute of Physics Publishing)  244 2010

Research paper (scientific journal), Joint Work, Accepted,  ISSN  1742-6596

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Positively charged excitonic state in single InAs quantum dot (QD) has been neutralized by Si delta doping and the optical properties of the fabricated samples are characterized by micro-photoluminescence measurements (μ-PL) at low temperature. An InAs QD sample having dominant emissions from positively charged excitonic states is prepared for a reference. By optimizing Si delta doping conditions, positively charged QDs are neutralized successfully and distinctive emissions from neutral exciton and biexciton from single QDs are achieved. For excessive doping condition, μ-PL spectra show optical degradation of lowering of peak intensity and broadening of peak width as doping concentration increases. © 2010 IOP Publishing Ltd.

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Zero-cell photonic crystal nanocavity laser with quantum dot gain

M Nomura, Y Ota, N Kumagai, S Iwamoto, Y Arakawa

Applied Physics Letters 97 (19), 191108 (AMER INST PHYSICS)  97 ( 19 )  2010

Research paper (scientific journal), Joint Work, Accepted,  ISSN  0003-6951

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We demonstrate laser oscillation in a hexagonal-lattice photonic crystal nanocavity using an InGaAs quantum dot gain material by optical pumping at 5 K. The cavity comprises a defect created by shifting several air holes in a two-dimensional photonic crystal slab structure without removing any air holes to achieve both small mode volume and a high cavity quality factor. The measured cavity quality factors and estimated mode volume for the nanocavity are similar to 33 000 and 0.004 mu m(3) [0.23(lambda(0)/n)(3)]. The laser threshold is compared between the zero-cell and L3-type nanocavity lasers, and the zero-cell nanolasers are found to have lower thresholds of about one-third of the L3-type nanolasers. This result suggests that a higher Purcell factor of the zero-cell nanolaser is reflected as a lower laser threshold. (C) 2010 American Institute of Physics. [doi:10.1063/1.3514556]

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Single quantum dot-photonic crystal nanocavity laser

M Nomura, N Kumagai, Y Ota, S Iwamoto, Y Arakawa

IEICE Technical Report; IEICE Tech. Rep. 109 (403), 11-14 (The Institute of Electronics, Information and Communication Engineers)  109 ( 401 ) 11 - 14 2010

Joint Work,  ISSN  0913-5685

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Strong light-matter interaction in a single semiconductor quantum dot-nanocavity coupled system provides various interesting physics, which can be described by cavity quantum electrodynamics. A single quantum dot-photonic crystal nanocavity system provides excellent test beds for solid cavity quantum electrodynamics because photons can be confined in ultimately small volume on the order of its wavelength. An ultimately small laser can be achievable by using a single quantum dot gain material in this system. Here we demonstrate laser oscillation in both weak- and strong-coupling regimes in this system. In the strong-coupling regime, quanta are coherently going back and forth between the excitonic and phonic states, while irreversible photon emission from an excitonic state occurs in the lasing regime. The onset of lasing in the strong-coupling regime is of great interest and its demonstration in solid state materials is reported for the first time.

Investigation of the Spectral Triplet in Strongly Coupled Quantum Dot-Nanocavity System

Yasutomo Ota, Naoto Kumagai, Shunsuke Ohkouchi, Masayuki Shirane, Masahiro Nomura, Satomi Ishida, Satoshi Iwamoto, Shinichi Yorozu, Yasuhiko Arakawa

APPLIED PHYSICS EXPRESS (JAPAN SOC APPLIED PHYSICS)  2 ( 12 )  2009.12

Research paper (scientific journal), Joint Work, Accepted,  ISSN  1882-0778

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We experimentally investigated the excitation power dependence of a strongly coupled quantum dot (QD)-photonic crystal nanocavity system by photoluminescence measurements. At a low excitation power regime, we observed a vacuum Rabi doublet emission at the QD-cavity resonance condition. With increasing excitation power, in addition to the doublet, a third emission peak appeared. This observed spectral change is unexpected from conventional atomic cavity quantum electrodynamics. The observations can be attributed to featured pumping processes in the semiconductor QD-cavity system. (C) 2009 The Japan Society of Applied Physics DOI: 10.1143/APEX.2.122301

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Vacuum Rabi splitting with a single quantum dot embedded in a H1 photonic crystal nanocavity

Yasutomo Ota, Masayuki Shirane, Masahiro Nomura, Naoto Kumagai, Satomi Ishida, Satoshi Iwamoto, Shinichi Yorozu, Yasuhiko Arakawa

APPLIED PHYSICS LETTERS (AMER INST PHYSICS)  94 ( 3 )  2009.01

Research paper (scientific journal), Joint Work, Accepted,  ISSN  0003-6951

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We report here the first observation of vacuum Rabi splitting in a single quantum dot (QD) embedded in a H1 photonic crystal nanocavity by photoluminescence measurement. The QD emission was tuned into a cavity mode by controlling the temperature. At the resonance condition, clear anticrossing with a Rabi splitting of similar to 124 mu eV was observed, where the cavity mode possesses the smallest mode volume V similar to 0.43(lambda/n)(3) among strongly coupled QD-cavity systems reported to date.

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Impact of electron-phonon interactions on quantum-dot cavity quantum electrodynamics

Y Ota, S Iwamoto, N Kumagai, Y Arakawa

arXiv preprint arXiv:0908.0788  2009

Research paper (scientific journal), Joint Work, Accepted

Photonic Crystal Nanocavity Laser with Single Quantum Dot Gain

Masahiro Nomura, Naoto Kumagai, Satoshi Iwamoto, Yasutomo Ota, Yasuhiko Arakawa

2009 CONFERENCE ON LASERS AND ELECTRO-OPTICS AND QUANTUM ELECTRONICS AND LASER SCIENCE CONFERENCE (CLEO/QELS 2009), VOLS 1-5 (IEEE)     626 - 627 2009

Research paper (scientific journal), Joint Work, Accepted,  ISSN  978-1-4244-5184-5

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We demonstrate a photonic crystal nanocavity laser essentially driven by single quantum dot gain. A diluted quantum dot density (similar to 0.4/cavity) resulted in clear single quantum dot feature and distinct phase transition in photon correlation measurements.

Photonic crystal nanocavity laser with a single quantum dot gain

M Nomura, N Kumagai, S Iwamoto, Y Ota, Y Arakawa

Optics Express 17 (18), 15975-15982 (OPTICAL SOC AMER)  17 ( 18 ) 15975 - 15982 2009

Research paper (scientific journal), Joint Work, Accepted,  ISSN  1094-4087

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We demonstrate a photonic crystal nanocavity laser essentially driven by a self-assembled InAs/GaAs single quantum dot gain. The investigated nanocavities contain only 0.4 quantum dots on an average; an ultra-low density quantum dot sample (1.5 x 10(8) cm(-2)) is used so that a single quantum dot can be isolated from the surrounding quantum dots. Laser oscillation begins at a pump power of 42 nW under resonant condition, while the far-detuning conditions require similar to 145 nW for lasing. This spectral detuning dependence of laser threshold indicates substantial contribution of the single quantum dot to the total gain. Moreover, photon correlation measurements show a distinct transition from anti-bunching to Poissonian via bunching with the increase of the excitation power, which is also an evidence of laser oscillation using the single quantum dot gain. (C) 2009 Optical Society of America

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Photonic band-edge micro lasers with quantum dot gain

M Nomura, S Iwamoto, A Tandaechanurat, Y Ota, N Kumagai, Y Arakawa

Optics express 17 (2), 640-648 (OPTICAL SOC AMER)  17 ( 2 ) 640 - 648 2009

Research paper (scientific journal), Joint Work, Accepted,  ISSN  1094-4087

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We demonstrate optically pumped continuous-wave photonic band-edge microlasers on a two-dimensional photonic crystal slab. Lasing was observed at a photonic band-edge, where the group velocity was significantly small near the K point of the band structure having a triangular lattice. Lasing was achieved by using a quantum dot gain material, which resulted in a significant decrease in the laser threshold, compared with photonic band-edge lasers using quantum well gain material. Extremely low laser thresholds of similar to 80 nW at 6 K was achieved. Lasing was observed in a defect-free photonic crystal as small as similar to 7 mu m square. (C) 2009 Optical Society of America

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Light-matter interaction in single quantum dot with photonic crystal nanocavity

Y Arakawa, M Nomura, S Iwamoto, Y Ota

Conference on Lasers and Electro-Optics/Pacific Rim, TuH2_2 (Optics InfoBase Conference Papers)   2009

Research paper (scientific journal), Joint Work, Accepted

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We discuss recent advances in light-matter interaction in a single quantum dot embedded with photonic crystal nanocavity, including demonstration of a transition from strong coupling regime to lasing oscillation by the single dot gain. © 2009 IEEE.

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Investigation of the spectral triplet in strongly coupled quantum dot–nanocavity system

Y Ota, N Kumagai, S Ohkouchi, M Shirane, M Nomura, S Ishida, ...

Applied physics express 2 (12), 122301  2009

Research paper (scientific journal), Joint Work, Accepted

Vacuum Rabi splitting with a single quantum dot embedded in a photonic crystal nanocavity

Y Ota, M Shirane, M Nomura, N Kumagai, S Ishida, S Iwamoto, S Yorozu, ...

Applied Physics Letters 94 (3), 033102  2009

Research paper (scientific journal), Joint Work, Accepted

Achievement of ultra-low threshold excitation power (8 nW) in a nearly-single quantum dot nanocavity laser

M Nomura, Y Ota, N Kumagai, S Iwamoto, Y Arakawa

Conference on lasers and Electro-Optics, CTuW3 (IEEE)     1714 - + 2008

Research paper (scientific journal), Joint Work, Accepted,  ISSN  978-1-55752-859-9

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We demonstrate photonic crystal nanocavity laser with nearly-single quantum dot gain. Continuous-wave lasing was achieved at photocarrier generation rate of 5 x 10(9)/s, corresponding to several carrier injection into nearly-single quantum dot.

Efficient excitation and emission of single quantum dot by simultaneous coupling to two different photonic crystal nanocavity modes

Y Ota, M Nomura, N Kumagai, K Watanabe, S Ishida, S Iwamoto, ...

Conference on Lasers and Electro-Optics, CTuW2 (IEEE)     1712 - + 2008

Research paper (scientific journal), Joint Work, Accepted,  ISSN  978-1-55752-859-9

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We utilized simultaneous coupling of higher and ground states of a single QD with two different resonant modes of a PhC nanocavity for efficient excitation and emission. Enhanced emission with strongly suppressed background was demonstrated.

Enhanced photon emission and absorption of single quantum dot in resonance with two modes in photonic crystal nanocavity

Y Ota, M Nomura, N Kumagai, K Watanabe, S Ishida, S Iwamoto, ...

Applied Physics Letters 93 (18), 183114 (AMER INST PHYSICS)  93 ( 18 )  2008

Research paper (scientific journal), Joint Work, Accepted,  ISSN  0003-6951

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We demonstrate simultaneous enhancement of photon emission and absorption of a single InGaAs self-assembled quantum dot (QD) in resonance with two modes in a photonic crystal nanocavity. The QD, whose ground and excited states are resonant, respectively, with the first and second lowest order cavity modes, is excited by cavity resonant excitation at the wavelength of the second order cavity mode and shows 180 times greater photon emission from the ground state than a bare QD. This large enhancement is attributed to a combination of Purcell effect, efficient photon extraction, and cavity resonant absorption enhancement.

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Refraction and diffraction by a metal-dielectric multilayered structure

S Kameda, Y Ohta, H Kikuta

JOSA A 25 (4), 903-910 (Journal of the Optical Society of America A: Optics and Image Science, and Vision)  25 ( 4 ) 903 - 910 2008

Research paper (scientific journal), Joint Work, Accepted,  ISSN  10847529

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An optical refraction prism consisting of metal and dielectric, subwavelength, periodic multilayered thin films has been proposed. The multilayered structure of metal and dielectric thin films has a cylindrical dispersion surface for TM polarized light. The light behaviors are very different from those of conventional glass prisms and photonic crystal superprisms. Refraction and diffraction of the light wave for the metal-dielectric multilayered prism has been investigated by numerical simulations and graphical representation based on the dispersion surface. A prism with 0.2 μm period had an angular dispersion of 0.20̊/nm for ̃0.8 μm wavelength light. The finite thick metal-dielectric multilayered structure acted as a slab waveguide. © 2008 Optical Society of America.

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Large vacuum Rabi splitting in single self-assembled quantum dot-nanocavity system

M Nomura, Y Ota, N Kumagai, S Iwamoto, Y Arakawa

Applied physics express 1 (7), 072102 (JAPAN SOCIETY APPLIED PHYSICS)  1 ( 7 )  2008

Research paper (scientific journal), Joint Work, Accepted,  ISSN  1882-0778

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We report on the observation of the strong-coupling regime in a single InGaAs self-assembled quantum dot (OD) and photonic crystal nanocavity system. There was a strong interaction between the OD exciton and discretized photon mode and the strong coupling was manifest in photoluminescence data, which displayed a distinct anti-crossing in temperature tuning measurements. A vacuum Rabi splitting of 180 mu eV was observed, which was larger than the values given in previous studies with clear exciton polariton modes. In addition, the exciton-photon coupling strength amounted to about 90 peV. A distinct energy mixing, which resulted from the reversible photon emission process of a OD, was also observed when the system formed a QD exciton polariton state. (C) 2008 The Japan Society of Applied Physics.

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Fabrication and characterization of photonic crystal nanocavity with degenerated cavity modes for generating entangled photon pairs using quantum dots

Y Ota, M Nomura, N Kumagai, K Watanabe, S Ishida, S Iwamoto, ...

Conference on Lasers and Electro-Optics/Pacific Rim, TuF4_6 (Optics InfoBase Conference Papers)   2007

Research paper (scientific journal), Joint Work, Accepted

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We successfully fabricated photonic crystal nanocavities for generating entangled photon pairs using single quantum dots. The fabricated cavities have a minimum splitting between two orthogonal dipole modes of-250 ieV and measured cavity Qs of-2,000. A maximum fidelity of 0.95 for entangled photon pairs is expected with this cavity. © CLEO Pacific Rim 2007.

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Fabrication of photonic crystal nanocavity for generating entangled photon pairs using quantum dots

Y Ota, M Nomura, N Kumagai, K Watanabe, S Ishida, S Iwamoto, ...

2007 International Nano-Optoelectronics Workshop, 226-227 (2007 International Nano-Optelectronics Workshop, iNOW)     226 - 227 2007

Research paper (scientific journal), Joint Work, Accepted

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We fabricated photonic crystal nanocavities which have two orthogonal dipole modes with a minimum splitting of ∼250 μeV and measured cavity Qs of -2,000. Those cavities are applicable for generating entangled photon pairs using quantum dots. © 2007 IEEE.

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Fabrication and characterization of photonic crystal nanocavity with degenerated cavity modes for generating entangled photon pairs using quantum dotsS

Yasutomo Ota, Masahiro Nomura, Naoto Kumagai, Katsuyuki Watanabe, Satomi Ishida, Satoshi Iwamoto, Masayuki Shirane, Shunsuke Kono, Shinichi Yorozu, Yasuhiko Arakawa

2007 PACIFIC RIM CONFERENCE ON LASERS AND ELECTRO-OPTICS, VOLS 1-4 (IEEE)     904 - + 2007

Research paper (scientific journal), Joint Work, Accepted,  ISSN  978-1-4244-1173-3

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We successftilly fabricated photonic crystal nanocavities for generating entangled photon pairs using single quantum dots. The fabricated cavities have a minimum splitting between two orthogonal dipole mode's of similar to 250 mu eV and measured cavity ( A of similar to 2,000. A maximum fidelity of 0,95 for entangled photon pairs is expected with this cavity.

Nanocavity laser with ultralow threshold

M Nomura, Y Ota, N Kumagai, S Iwamoto, Y Arakawa

IEICE Technical Report; IEICE Tech. Rep. 107 (372), 1-6 (The Institute of Electronics, Information and Communication Engineers)  107 ( 372 ) 1 - 6 2007

Joint Work,  ISSN  0913-5685

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A coupling system of quantum dots and nanocavity realizes strong light-matter interaction. The unique physics in this system is based on the cavity quantum electrodynamics. A nanocavity laser with an ultralow threshold can be achieved by using quantum dots and a photonic crystal nanocavity with strong photon confinement. We have reported the first achievement of continuous-wave lasing of an optically pumped photonic crystal (PhC) nanocavity laser operating at room temperature. Further improvement of nano-fabrication technology results in smaller threshold power of the order of 1μW. We also report theoretical analysis based on quantum optics to obtain prerequisites of nanocavity, such as Q value and positioning accuracy, for single quantum dot laser, which is one of the forms of ultimate lasers.

Epitaxial growth of an Sm2O3 buffer layer for EuBa2Cu3O7-delta thin films by magnetron sputtering

Kimura Y., Ota Y., Michikami O.

PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS 445   833 - 836 2006.10

Research paper (scientific journal), Joint Work, Accepted,  ISSN  0921-4534

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Refraction and diffraction by a metal and dielectric multilayered prism

H Kikuta, Y Ohta, S Kameda

Organic Photonics and Electronics, JSuA14 (Optics InfoBase Conference Papers)   2006

Research paper (scientific journal), Joint Work, Accepted

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A multilayered structure of metal and dielectric thin-films has a cylindrical dispersion surface for TM polarized light. Refraction and diffraction of the light wave in a metal/dielectric multilayered prism has been investigated. © 2005 Optical Society of America.

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