Papers - Ota, Yasutomo

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

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

Optics Express 32 ( 4 ) 6382 - 6390 2024.02

Research paper (scientific journal), Joint Work, Accepted

　View Summary

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 n<inf>g</inf> = 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 n<inf>g</inf> = 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.

• Access to Document (DOI)

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

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

Optics Express 82 ( 3 ) 4295 - 4304 2024.01

Research paper (scientific journal), Joint Work, Accepted

　View Summary

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.

• Access to Document (DOI)

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 12 ( 2 )  2024.01

Research paper (scientific journal), Joint Work, Accepted

　View Summary

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.

• Access to Document (DOI)

Demonstration of Magneto-optical Microdisk Resonators Based on Yttrium Iron Garnet

Yambe T., Kitai T., Taniguchi K., Gao S., Imamura R., Kumazaki H., Fujii S., Iwamoto S., Tanabe T., Ota Y.

Conference on Lasers and Electro Optics Pacific Rim CLEO PR 2024 in Proceedings 2024 Conference on Lasers and Electro Optics Pacific Rim CLEO PR  2024

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

　View Summary

A microdisk resona tor ba sed on monocrysta lline yttrium iron ga rnet is reported. The 100-μm-dia meter microdisk in a 300-nm-thick ga rnet film a llows tight spa tia l confinement to enha nce ma gneto-optica l intera ctions. Experimenta lly, we observed a high Q of 2.1 × 10⁴.

Optical skyrmion beam generation based on integrated photonics

Iwamoto S., Lin W., Ota Y.

Jsap Optica Joint Symposia Jsap 2024 in Proceedings Jsap Optica Joint Symposia 2024 Abstracts  2024

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

Observation of Su-Schrieffer-Heeger Topological Model Band Structure in Integrated LNOI Coupled Ring Cavities

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

16th Pacific Rim Conference on Lasers and Electro Optics CLEO PR 2024  2024

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

　View Summary

We report synthetic frequency dimension Su-Schrieffer-Heeger model and its band structure observation using coupled ring cavities on an integrated photonic chip. Intra-cell and inter-cell couplings between hybridized modes are controlled using radio frequency electrooptic modulation. optic modulation.

• Access to Document (DOI)

Observation of Su-Schrieffer-Heeger Topological Model Band Structure in Integrated LNOI Coupled Ring Cavities

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

Conference on Lasers and Electro Optics Pacific Rim CLEO PR 2024 in Proceedings 2024 Conference on Lasers and Electro Optics Pacific Rim CLEO PR  2024

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

　View Summary

We report synthetic frequency dimension Su-Schrieffer-Heeger model and its band structure observation using coupled ring cavities on an integrated photonic chip. Intra-cell and inter-cell couplings between hybridized modes are controlled using radio frequency electro-optic modulation.

Micro-Transfer-Printed Membrane Lasers on Si platform

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

Proceedings of SPIE the International Society for Optical Engineering 12905 2024

Research paper (international conference proceedings), Joint Work, Accepted,  ISSN  0277786X

　View Summary

We fabricate directly modulated membrane distributed-reflector lasers on a Si platform using a micro-transfer printing method. Single-mode lasing with a low threshold current of 1.2 mA and 50-Gbaud-class direct modulation are demonstrated.

• Access to Document (DOI)

Membrane Directly Modulated Lasers on Si Using Micro-Transfer Printing Integrated with Post-Processed Polymer Waveguide

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

Conference Digest IEEE International Semiconductor Laser Conference  2024

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

　View Summary

We fabricate directly modulated membrane lasers by micro-transfer printing and integrate a single-mode polymer waveguide after printing. An InP inverse taper waveguide is used as a spot-size converter for the polymer waveguide. Fiber-coupled mW-class output power and 100-Gbit/s signal modulation are achieved.

• Access to Document (DOI)

Measurement of Synthetic-Dimension Band Structures in Silicon Coupled Ring Resonators

Zhang R., Li L., Kamata M., Baba T., Ozawa T., Ota Y., Iwamoto S.

16th Pacific Rim Conference on Lasers and Electro Optics CLEO PR 2024  2024

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

　View Summary

We fabricated integrated silicon coupled-ring resonators and measured photonic band structures for synthetic frequency lattices with different configurations. A phase difference between two modulation signals introduced a synthetic gauge flux, resulting in asymmetric band structures.

• Access to Document (DOI)

Measurement of Synthetic-Dimension Band Structures in Silicon Coupled Ring Resonators

Zhang R., Li L., Kamata M., Baba T., Ozawa T., Ota Y., Iwamoto S.

Conference on Lasers and Electro Optics Pacific Rim CLEO PR 2024 in Proceedings 2024 Conference on Lasers and Electro Optics Pacific Rim CLEO PR  2024

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

　View Summary

We fabricated integrated silicon coupled-ring resonators and measured photonic band structures for synthetic frequency lattices with different configurations. A phase difference between two modulation signals introduced a synthetic gauge flux, resulting in asymmetric band structures.

Investigation of one-dimensional moiré photonic crystal nanobeam cavities

Ito T., Ishii Y., Trushin S.M., Lu G., Iwamoto S., Ota Y.

Conference on Lasers and Electro Optics Pacific Rim CLEO PR 2024 in Proceedings 2024 Conference on Lasers and Electro Optics Pacific Rim CLEO PR  2024

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

　View Summary

We designed nanobeam optical cavities based on moiré photonic crystals. An exponential increase of the Q factor as high as 10⁷ with increasing moiré period was observed, while the mode volume remained small around 0.5(λ/η)³.

Flat band light localization in one dimensional moiré bilayer photonic crystals with staggered potential

Trushin S.M., Ishii Y., Ito T., Iwamoto S., Ota Y.

Conference on Lasers and Electro Optics Pacific Rim CLEO PR 2024 in Proceedings 2024 Conference on Lasers and Electro Optics Pacific Rim CLEO PR  2024

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

　View Summary

We demonstrate that double periodic modulations improve flat band light localization in bilayer one-dimensional moiré photonic crystals. Flatter optical bands were observed even at zero interlayer distance, accelerating their experimental realization and nanophotonics applications.

Fabrication of Photonic Crystal Nanocavities based on Monocrystalline Yttrium Iron Garnet

Taniguchi K., Kitai T., Yambe T., Gao S., Iwamoto S., Ota Y.

Conference on Lasers and Electro Optics Pacific Rim CLEO PR 2024 in Proceedings 2024 Conference on Lasers and Electro Optics Pacific Rim CLEO PR  2024

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

　View Summary

We report the fabrication of air-suspended photonic crystal nanocavities based on single-crystalline yttrium iron garnet (YIG). The unprecedented high-quality photonic nanostructures based on YIG will open the novel path to magneto-nanophotonics and quantum magnonics.

Photonic Frequency Space Simulation of Tight-Binding Lattices Using Integrated LNOI Ring Resonators

Balčytis A., Dinh H., Ozawa T., Ota Y., Baba T., Iwamoto S., Mitchell A., Nguyen T.G.

Conference on Lasers and Electro Optics Pacific Rim CLEO PR 2024 in Proceedings 2024 Conference on Lasers and Electro Optics Pacific Rim CLEO PR  2024

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

　View Summary

We use electro-optically modulated ring cavities, integrated on thin-film lithium niobate, to model frequency dimension tight-binding lattices with versatile connectivity. Inter-mode coupling range, strength, and hopping phase are controlled via the modulating radio frequency signals.

Uncooled Operation of Directly Modulated Membrane Laser with Buried Sapphire Layer on Si Substrate

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

Optical Fiber Communication Conference in Proceedings Optical Fiber Communication Conference Ofc 2024  2024

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

　View Summary

A membrane laser with a buried sapphire layer on Si has 3-dB bandwidths of 40-25 GHz at 25-80̊C. The laser demonstrates 80-Gbit/s PAM4 operations up to 80̊C at an energy cost of 0.77 pJ/bit.

• Access to Document (DOI)

Uncooled Operation of Directly Modulated Membrane Laser with Buried Sapphire Layer on Si Substrate

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

2024 Optical Fiber Communications Conference and Exhibition Ofc 2024 Proceedings  2024

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

　View Summary

A membrane laser with a buried sapphire layer on Si has 3-dB bandwidths of 40-25 GHz at 25-80°C. The laser demonstrates 80-Gbit/s PAM4 operations up to 80°C at an energy cost of 0.77 pJ/bit.

Transfer-printed Si waveguides on Er:YSO crystals toward efficient quantum media conversion

Okajima T., Ohta R., Sato T., Tachizaki Y., Xu X., Okamoto H., Ota Y.

Conference on Lasers and Electro Optics Pacific Rim CLEO PR 2024 in Proceedings 2024 Conference on Lasers and Electro Optics Pacific Rim CLEO PR  2024

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

　View Summary

We demonstrate the transfer-printing integration of silicon waveguides on Er:YSO crystals. The versatile integration technique, together with strong optical interactions with Er ions through the confined photons, facilitates the development of efficient spin-photon converters.

Transfer Printed InP-based Membrane Laser on Sapphire-Si Bonded Substrate

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

IEEE International Conference on Group IV Photonics Gfp  2024

Research paper (international conference proceedings), Joint Work, Accepted,  ISSN  19492081

　View Summary

An InP-based membrane laser is transfer-printed onto a thin sapphire on a Si substrate. Thanks to the low refractive index and high thermal conductivity of the sapphire, the fabricated laser has a 3-dB bandwidth of 26 GHz and performs 53.125-Gbit/s operations at 50 degrees Celsius.

• Access to Document (DOI)

Photonic Frequency Space Simulation of Tight-Binding Lattices Using Integrated LNOI Ring Resonators

Balčytis A., Dinh H., Ozawa T., Ota Y., Baba T., Iwamoto S., Mitchell A., Nguyen T.G.

16th Pacific Rim Conference on Lasers and Electro Optics CLEO PR 2024  2024

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

　View Summary

We use electro-optically modulated ring cavities, integrated on thin-film lithium niobate, to model frequency dimension tight-binding lattices with versatile connectivity. Inter-mode coupling range, strength, and hopping phase are controlled via the modulating radio frequency signals.

• Access to Document (DOI)