Papers - Ota, Yasutomo

High-temperature Operation of Membrane DR Lasers Integrated with Si Waveguide by Micro-transfer Printing Method

Maeda Y., Aihara T., Fujii T., Hiraki T., Takeda K., Tsuchizawa T., Sugiyama H., Sato T., Segawa T., Ota Y., Iwamoto S., Arakawa Y., Matsuo S.

Conference Digest IEEE International Semiconductor Laser Conference 2022-October 2022

Research paper (international conference proceedings), Joint Work, Accepted,  ISSN  08999406

　View Summary

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.

• Access to Document (DOI)

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

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

　View Summary

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.

• Access to Document (DOI)

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

Tian F., Ota Y., Iwamoto S.

Optics Infobase Conference Papers  2022

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

　View Summary

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.

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

Gao S., Ota Y., Liu T., Iwamoto S.

Optics Infobase Conference Papers  2022

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

　View Summary

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.

• Access to Document (DOI)

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

Gao S., Ota Y., Liu T., Iwamoto S.

2022 Conference on Lasers and Electro Optics Pacific Rim CLEO PR 2022 Proceedings  2022

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

　View Summary

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.

• Access to Document (DOI)

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

Pholsen N., Ota Y., Iwamoto S.

Conference Digest IEEE International Semiconductor Laser Conference 2022-October 2022

Research paper (international conference proceedings), Joint Work, Accepted,  ISSN  08999406

　View Summary

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.

• Access to Document (DOI)

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  2022

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

　View Summary

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.

• Access to Document (DOI)

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

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

　View Summary

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.

• Access to Document (DOI)

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

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

　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.

• Access to Document (DOI)

Semiconductor topological nanophotonics incorporating light emitters

Ota Y., Arakawa Y., Iwamoto S.

International Conference on Metamaterials Photonic Crystals and Plasmonics    412 - 413 2022

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

　View Summary

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.

Topological modes observed in Si photonics SSH integrated circuit

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

Optics Infobase Conference Papers  2022

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

　View Summary

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.

• Access to Document (DOI)

Topological modes observed in Si photonics SSH integrated circuit

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

2022 Conference on Lasers and Electro Optics Pacific Rim CLEO PR 2022 Proceedings  2022

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

　View Summary

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.

• Access to Document (DOI)

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

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

Physical Review Research 3 ( 4 )  2021.12

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.

• Access to Document (DOI)

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

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

Optics Express 29 ( 23 ) 23 - 25 2021.11

Research paper (scientific journal), Joint Work, Accepted

　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.

• Access to Document (DOI)

Single photon generation in a topological slow light waveguide

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

2021 Conference on Lasers and Electro Optics CLEO 2021 Proceedings  2021.05

Research paper (international conference proceedings), 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.

Synthetic Dimension Photonics on a Si CMOS Platform

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

2021 Conference on Lasers and Electro Optics CLEO 2021 Proceedings  2021.05

Research paper (international conference proceedings), 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.

Experimental demonstration of topological slow light waveguides in valley photonic crystals

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

Optics Express 29 ( 9 ) 13441 - 13450 2021.04

Research paper (scientific journal), Joint Work, Accepted

　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.

• Access to Document (DOI)

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

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

Physical Review Research 3 ( 2 )  2021.04

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

　View Summary

A full Poincaré (FP) beam possesses all possible optical spin states in its cross section, which constitutes an optical analog 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.

• Access to Document (DOI)

Fabrication of valley photonic crystals with CMOS-compatible process

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

26th Microoptics Conference Moc 2021  2021

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

　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.

• Access to Document (DOI)

One-side excited one-way modes in nonreciprocal waveguides

Liu T., Ota Y., Iwamoto S.

Optics Infobase Conference Papers  2021

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