Papers - Ota, Yasutomo

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

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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

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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

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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

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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

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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

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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

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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

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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

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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

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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

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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

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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