Papers - Ota, Yasutomo

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

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

Optics Letters 44 ( 15 ) 3749 - 3752 2019.08

Research paper (scientific journal), Joint Work, Accepted,  ISSN  01469592

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In this study, we examine a photonic wire waveguide embedded with an ensemble of quantum dots (QDs) that directionally emits into the waveguide depending on the spin state of the ensemble. The directional emission is facilitated by the spin-orbit interaction of light. The waveguide has a two-step stair-like cross section and QDs are embedded 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, which supports selective coupling of the QD ensemble radiation into a whispering gallery mode that rotates unidirectionally. Our study provides a foundation for spin-dependent optoelectronic devices.

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Photonic crystal nanocavity based on a topological corner state

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

Optica 6 ( 6 ) 786 - 789 2019.06

Research paper (scientific journal), Joint Work, Accepted,  ISSN  23342536

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

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

Applied Physics Express 12 ( 6 )  2019.06

Research paper (scientific journal), Joint Work, Accepted,  ISSN  18820778

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We report a valley photonic crystal (VPhC) waveguide in a GaAs slab with InAs quantum dots (QDs) as an internal light source exploited for the 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 the near-infrared light emitted from the QDs, even with the presence of sharp bends, due to 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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Single Plasmon Generation in an InAs/GaAs Quantum Dot in a Transfer-Printed Plasmonic Microring Resonator

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

ACS Photonics 6 ( 5 ) 1106 - 1110 2019.05

Research paper (scientific journal), Joint Work, Accepted

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We report single plasmon generation with a self-assembled InAs/GaAs quantum dot embedded in a plasmonic microring resonator. The plasmonic cavity based on a GaAs microring is defined on an atomically smooth silver surface. We fabricated this structure with the help of transfer printing, which enables the pick-and-place assembly of the complicated, heterogeneous three-dimensional stack. We show that a high-order surface-plasmon-polariton transverse mode mediates efficient coupling between the InAs/GaAs quantum dots and the plasmonic cavity, paving the way for developing plasmonic quantum light sources based on the state-of-the-art solid-state quantum emitters. Experimentally, we observed Purcell-enhanced radiation from the quantum dot coupled to the plasmonic mode. We also observed a strong antibunching in the intensity correlation histogram measured for scattered photons from the plasmonic resonator, indicating single plasmon generation in the resonator. Our results are important for the development of quantum plasmonic circuits integrating high-performance single plasmon generators.

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Nanocavity Based on a Topological Corner State in a Two-Dimensional Photonic Crystal

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

2019 Conference on Lasers and Electro Optics CLEO 2019 Proceedings  2019.05

Research paper (international conference proceedings), Joint Work, Accepted

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

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

2019 Conference on Lasers and Electro Optics CLEO 2019 Proceedings  2019.05

Research paper (international conference proceedings), Joint Work, Accepted

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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.

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

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

Optica 6 ( 3 ) 296 - 299 2019.03

Research paper (scientific journal), Joint Work, Accepted,  ISSN  23342536

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Three-dimensional (3D) integration of photonic devices is an ultimate route toward highly integrated photonic circuits. 3D photonic crystals (PCs) are a promising platform for 3D integration because of their complete photonic bandgaps (cPBGs) which enables full control of light. However, simultaneous integration of active and passive devices into a 3D PC has been hindered due to fabrication difficulties. Here, we simultaneously integrate a nanocavity laser and waveguides into a 3D PC with a cPBG at near-IR wavelengths using micromanipu-lation technology. The proposed plate-insertion stacking method allowed fabrication of 3D PCs with a large number of layers, enabling integration of the active and passive circuit components. Laser emission from the photo-excited nanocavity laser was observed from the output port of the waveguides, demonstrating successful guiding of the light from the nanocavity laser in the 3D PC. This work paves the way for 3D photonic circuits using 3D PCs with cPBGs.

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

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

APL Photonics 4 ( 3 )  2019.03

Research paper (scientific journal), Joint Work, Accepted

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Silicon photonics is a powerful platform for implementing large-scale photonic integrated circuits (PICs) because of its compatibility with mature complementary-metal-oxide-semiconductor (CMOS) technology. Exploiting silicon-based PICs for quantum photonic information processing (or the so-called silicon quantum photonics) provides a promising pathway for large-scale quantum applications. For the development of scalable silicon quantum PICs, a major challenge is integrating on-silicon quantum light sources that deterministically emit single photons. In this regard, the use of epitaxial InAs/GaAs quantum dots (QDs) is a very promising approach because of their capability of deterministic single-photon emission with high purity and indistinguishability. However, the required hybrid integration is inherently difficult and often lacks the compatibility with CMOS processes. Here, we demonstrate a QD single-photon source integrated on a glass-clad silicon photonic waveguide processed by a CMOS foundry. Hybrid integration is performed using transfer printing, which enables us to integrate heterogeneous optical components in a simple pick-and-place manner and thus assemble them after the entire CMOS process is completed. We observe single-photon emission from the integrated QD and its efficient coupling into the silicon waveguide. Our transfer-printing-based approach is fully compatible with CMOS back-end processes and thus will open the possibility for realizing large-scale quantum PICs that leverage CMOS technology.

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

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

Physical Review Applied 11 ( 2 )  2019.02

Research paper (scientific journal), Joint Work, Accepted

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A 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 QPICs to facilitate photon-photon interaction. However, to date, realization of optical elements with deterministic (i.e., not probabilistic) single-photon nonlinearity by use of silicon-based components is challenging despite the enhancement of the functionality of QPICs based on silicon photonics. In this study, we realize a strongly coupled InAs/GaAs quantum-dot-cavity-quantum-electrodynamics 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-quantum-electrodynamics system on the CMOS photonic chip realized in this work is a promising candidate for an on-chip single-photon nonlinear element, which constitutes the fundamental component for future applications based on QPICs, such as coherent manipulation and nondestructive measurement of qubit states via a cavity, and an efficient single-photon filter and router.

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

Zon , Phienlumlert P., Thainoi S., Kiravittaya S., Tandaechanurat A., Nuntawong N., Sopitpan S., Yordsri V., Thanachayanont C., Kanjanachuchai S., Ratanathammaphan S., Panyakeow S., Ota Y., Iwamoto S., Arakawa Y.

Physica Status Solidi A Applications and Materials Science 216 ( 1 )  2019.01

Research paper (scientific journal), Joint Work, Accepted,  ISSN  18626300

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Tuning growth of nanostructures can provide additional routes to engineer their characteristics. In this work, the authors report on a combined growth of GaSb/GaAs quantum dots (QDs) and growth of GaAs on (001) Ge substrate. Surface decorated with GaAs anti-phase domain is the initial template to investigate the growth-rate effects on the growth of self-assembled GaSb QDs. By varying the GaSb growth rates, QD ensembles with different morphologies are formed. Perpendicular alignment of elongated GaSb QDs is observed. Cross-sectional transmission electron microscopic images show a substantial reduction of lateral QD size when it is buried in GaAs matrix. Raman scattering as well as power-dependent photoluminescence spectroscopies are performed to reveal the optical properties of the nanostructures. Type-II band alignment characteristic is confirmed.

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Hybrid integration of quantum dot-nanocavity systems on silicon

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

Optics Infobase Conference Papers Part F144-FiO 2019 2019

Research paper (international conference proceedings), Joint Work, Accepted

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

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

Optics Infobase Conference Papers Part F129-CLEO_SI 2019 2019

Research paper (international conference proceedings), Joint Work, Accepted

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

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

Optics Infobase Conference Papers Part F128-CLEO_QELS 2019 2019

Research paper (international conference proceedings), Joint Work, Accepted

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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.

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Topological photonic crystal nanocavity laser

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

Communications Physics 1 ( 1 )  2018.12

Research paper (scientific journal), Joint Work, Accepted

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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 microscale 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.

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

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

Optics Express 26 ( 16 ) 21219 - 21234 2018.08

Research paper (scientific journal), Joint Work, Accepted

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Light with nonzero orbital angular momentum (OAM) or twisted light is promising for quantum communication applications such as OAM-entangled photonic qubits. Methods and devices for the conversion of the photonic OAM to photonic spin angular momentum (SAM), as well as for the photonic SAM to electronic SAM transformation are known but the direct conversion between the photonic OAM and electronic SAM is not available 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. The confined spin-polarized electrons could recombine with holes to give circularly polarized emission, which could 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 with a 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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Lasing in a topological photonic crystal nanocavity

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

2018 Conference on Lasers and Electro Optics CLEO 2018 Proceedings  2018.08

Research paper (international conference proceedings), Joint Work, Accepted

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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.

Quantum dot single photon sources transfer-printed on wire waveguides

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

2018 Conference on Lasers and Electro Optics CLEO 2018 Proceedings  2018.08

Research paper (international conference proceedings), Joint Work, Accepted

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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 >60% is experimentally demonstrated.

Quantum-dot nanolasers on Si photonic circuits

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

2018 Conference on Lasers and Electro Optics CLEO 2018 Proceedings  2018.08

Research paper (international conference proceedings), Joint Work, Accepted

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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.

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

Vo Q.H., Ota Y., Watanabe K., Kageyama T., Iwamoto S., Arakawa Y.

Japanese Journal of Applied Physics 57 ( 8 )  2018.08

Research paper (scientific journal), Joint Work, Accepted,  ISSN  00214922

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We demonstrate two dimensional photonic crystal nanocavities embedding spatially-isolated active regions containing InAs/GaAs self-assembled quantum dots. We fabricated the GaAs-based structures by a combination of electron-beam lithography, dry/wet etching and crystal regrowth using molecular beam epitaxy. The fabricated nanocavity based on a photonic crystal double heterostructure supports a cavity mode with a high experimental quality factor over 10,000, despite the existence of a mound structure on the nanocavity formed during the regrowth. Using electromagnetic simulations, we discuss the origin of the cavity mode and a direction for further increasing the quality factor. The two dimensional photonic crystal nanocavities with buried quantum dot active regions will provide a useful platform for developing high performance nanolasers.

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Advanced photonic crystal nanocavity quantum dot lasers

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

IEICE Transactions on Electronics E101C ( 7 ) 553 - 560 2018.07

Research paper (scientific journal), Joint Work, Accepted,  ISSN  09168524

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We discuss our recent progress in photonic crystal nanocavity quantum dot lasers. We show how enhanced light matter interactions in the nanocavity lead to diverse and fascinating lasing phenomena that are in general inaccessible by conventional bulky semiconductor lasers. First, we demonstrate thresholdless lasing, in which any clear kink in the output laser curve does not appear. This is a result of near unity coupling of spontaneous emission into the lasing cavity mode, enabled by the strong Purcell effect supported in the nanocavity. Then, we discuss self-frequency conversion nanolasers, in which both near infrared lasing oscillation and nonlinear optical frequency conversion to visible light are simultaneously supported in the individual nanocavity. Owing to the tight optical confinement both in time and space, a high normalized conversion efficiency over a few hundred %/W is demonstrated. We also show that the intracavity nonlinear frequency conversion can be utilized to measure the statistics of the intracavity photons. These novel phenomena will be useful for developing various nano-optoelectronic devices with advanced functionalities.

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