Papers - Tanabe, Takasumi

Saturable Absorption of CNT and Fabrication of Erbium-doped Microresonator for On-chip Mode-locked Laser

Imamura R., Suzuki T.S.L.P., Ishida R., Fujii S., Set S.Y., Yamashita S., Tanabe T.

IEEJ Transactions on Electronics, Information and Systems 142 ( 3 ) 395 - 400 2022

ISSN  03854221

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Mode-locked fiber lasers are gaining a lot of attention in the industry because of their excellent performance while being relatively inexpensive. Although fiber ring is robust and has been widely used, it only achieves a repetition rate of several hundreds of MHz due to the long fiber needed to build the resonator. On the other hand, Whispering-Gallery-Mode (WGM) microresonators can achieve an extremely high repetition rate due to the smallness of the device. We explore the possibility of a passively mode-locked laser with CNTs as a saturable absorber and erbium-doped microresonator.

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Multi-wavelength reconstruction in a compact (< mm) high-resolution (< 0.1 nm) random photonic crystal spectrometer

Kodama T., Sugano R., Hofs J., Ohtsuka M., Seki M., Yokoyama N., Okano M., Tanabe T.

Optics InfoBase Conference Papers  2022

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We experimentally demonstrate the reconstruction of multiple wavelength light with an ultra-compact spectrometer. The spectrometer is based on a random photonic crystal and operates with a spectral resolution beyond the fabrication error.

Multi-wavelength reconstruction in a compact (< mm) high-resolution (< 0.1 nm) random photonic crystal spectrometer

Kodama T., Sugano R., Hofs J., Ohtsuka M., Seki M., Yokoyama N., Okano M., Tanabe T.

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

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We experimentally demonstrate the reconstruction of multiple wavelength light with an ultra-compact spectrometer. The spectrometer is based on a random photonic crystal and operates with a spectral resolution beyond the fabrication error.

Mode-locked Operation in a Coupled Microresonator System with Gain and Nonlinear Loss

Imamura R., Tate Y., Nakashima A., Nagashima K., Fujii S., Tanabe T.

Optics InfoBase Conference Papers  2022

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We numerically study the mode-locking behavior in a system in which an erbium-doped resonator (gain) is coupled to a carbon-nanotube functionalized resonator (nonlinear loss). We find that mode-locking is possible even with a small gain and relatively low Q by adjusting the coupling between two cavities.

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Mode-locked Operation in a Coupled Microresonator System with Gain and Nonlinear Loss

Imamura R., Tate Y., Nakashima A., Nagashima K., Fujii S., Tanabe T.

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

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We numerically study the mode-locking behavior in a system in which an erbium-doped resonator (gain) is coupled to a carbon-nanotube functionalized resonator (nonlinear loss). We find that mode-locking is possible even with a small gain and relatively low Q by adjusting the coupling between two cavities.

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Low-cost photonic crystal spectrometer using up-conversion

Sugano R., Jin S., Hofs J., Yube K., Nagashima K., Kodama T., Tanabe T.

Optics InfoBase Conference Papers  2022

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We used up-conversion to capture the localized light of a photonic crystal spectrometer with an inexpensive CMOS camera. We employed this data to detect a single wavelength using deep learning.

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Low-cost photonic crystal spectrometer using up-conversion

Sugano R., Jin S., Hofs J., Yube K., Nagashima K., Kodama T., Tanabe T.

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

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We used up-conversion to capture the localized light of a photonic crystal spectrometer with an inexpensive CMOS camera. We employed this data to detect a single wavelength using deep learning.

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Frequency comb generation in a silicon nitride microring resonator fabricated by using hot-wire CVD method

Sota S., Handa K., Tanabe T., Uzawa Y., Furusawa K., Sekine N.

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

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We report frequency comb generation in a silicon nitride (SiN) based microring resonator fabricated by the hot-wire chemical vapor deposition (HW-CVD) method with an intrinsic quality factor in excess of 5×105,.

Frequency comb generation in a silicon nitride microring resonator fabricated by using hot-wire CVD method

Sota S., Handa K., Tanabe T., Uzawa Y., Furusawa K., Sekine N.

Optics InfoBase Conference Papers  2022

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We report frequency comb generation in a silicon nitride (SiN) based microring resonator fabricated by the hot-wire chemical vapor deposition (HW-CVD) method with an intrinsic quality factor in excess of 5×105

FEC-free optical data transmission with a chip-integrated microresonator frequency comb source

Kogure S., Ohtsuka T., Fujii S., Kumazaki H., Tanaka S., Hashimoto Y., Kobayashi Y., Araki T., Furusawa K., Sekine N., Tanabe T.

Optics InfoBase Conference Papers  2022

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We investigated the feasibility of IM-DD communication in a microcomb. Turing pattern and soliton combs are ideal, though MI comb can transmit signals when the pump-detuning is well controlled and excessive noise is suppressed.

FEC-free optical data transmission with a chip-integrated microresonator frequency comb source

Kogure S., Ohtsuka T., Fujii S., Kumazaki H., Tanaka S., Hashimoto Y., Kobayashi Y., Araki T., Furusawa K., Sekine N., Tanabe T.

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

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We investigated the feasibility of IM-DD communication in a microcomb. Turing pattern and soliton combs are ideal, though MI comb can transmit signals when the pump-detuning is well controlled and excessive noise is suppressed.

FEC-free dense WDM transmission with Kerr soliton microcombs in crystalline MgF<inf>2</inf> microresonators

Tanikawa K., Tasaka S., Fujii S., Tanaka S., Kumazaki H., Wada K., Kogure S., Kawanishi S., Tanabe T.

Optics InfoBase Conference Papers  2022

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We demonstrated forward-error-correction (FEC)-free dense wavelength division multiplexing communication utilizing a Kerr soliton frequency comb generated from a high-Q crystalline microresonator with a 20-GHz free spectral range.

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FEC-free dense WDM transmission with Kerr soliton microcombs in crystalline MgF<inf>2</inf> microresonators

Tanikawa K., Tasaka S., Fujii S., Tanaka S., Kumazaki H., Wada K., Kogure S., Kawanishi S., Tanabe T.

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

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We demonstrated forward-error-correction (FEC)-free dense wavelength division multiplexing communication utilizing a Kerr soliton frequency comb generated from a high-Q crystalline microresonator with a 20-GHz free spectral range.

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Experimental investigation of Raman comb formation and stability in a silica microrod resonator

Sugawara S., Fujii S., Kumazaki H., Shota S., Tanabe T.

Optics InfoBase Conference Papers  2022

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We investigated the stability mechanism of a Raman comb by measuring RF beat noise and dispersion. Our measurements suggest that the Raman comb is stable even when only the stimulated Raman process is present.

Enhancing the wavelength resolution of a chirped photonic crystal waveguide based spectrometer by employing fabrication error

Tanabe T., Kodama T., Sugano R.

International Conference on Metamaterials, Photonic Crystals and Plasmonics    213 - 214 2022

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The presence of fabrication errors often degrades the performance of nanophotonic devices. Fabrication errors in the photonic crystal waveguide often appear as the Anderson localization of light. We show that the random localization of light can enhance the resolution of a photonic crystal spectrometer by utilizing this localization information in advance of the measurement.

Effect of detuning on noise characteristics in a microcomb-based light source

Kogure S., Fujii S., Kumazaki H., Sota S., Hashimoto Y., Kobayashi Y., Araki T., Tanabe T.

Optics InfoBase Conference Papers  2022

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We investigated the pump effective detuning dependence of noise and linewidth characteristics of modulation instability combs. Modulation instability combs are useful for applications if the detuning is smaller than several times the resonace linewidth.

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Design of a passively mode-locking whispering-gallery-mode microlaser

Suzuki T.P.S.L., Nakashima A., Nagashima K., Ishida R., Imamura R., Fujii S., Set S.Y., Yamashita S., Tanabe T.

Journal of the Optical Society of America B: Optical Physics 38 ( 10 ) 3172 - 3178 2021.10

ISSN  07403224

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Ultrahigh-repetition-rate lasers will become vital light sources for many future technologies; however, their realization is challenging because the cavity size must be minimized. Whispering-gallery-mode (WGM) microresonators are attractive for this purpose since they allow the strong light–matter interaction usually needed to enable mode locking. However, the optimum parameter ranges are entirely unknown since no experiments have yet been conducted. Here, we numerically investigate pulsed operation in a toroidal WGM microresonator with gain and saturable absorption (SA) to study the experimental feasibility. We show that dispersion is the key parameter for achieving passive mode locking in this system. Moreover, the design guideline provided in this work can apply to any small resonators with gain and SA and is not limited to a specific cavity system.

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Design of a Passively Mode-locked Microlaser with an Er-doped Microcavity and Carbon Nanotubes

Imamura R., Nakashima A., Nagashima K., Prugger Suzuki T.S.L., Ishida R., Fujii S., Tanabe T.

2021 Conference on Lasers and Electro-Optics Europe and European Quantum Electronics Conference, CLEO/Europe-EQEC 2021  2021.06

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Ultrahigh repetition rate lasers will become vital light sources for many technologies; however, they are difficult to realize because the cavity must be miniaturized. A mode-locked laser with whispering-gallery-mode (WGM) microresonators would provide a cost-effective on-chip solution that would allow us to demonstrate ultra-high repetition rate lasers. However, the required parameters, such as the cavity size, dispersion, minimum gain, and amount of saturable absorption (SA) loss, are unknown; we need to establish a clear guideline if we wish to discuss experimental feasibility and achieve mode locking (ML). Here, we report on a numerical investigation that clarified the optimum design parameters to achieve passive ML with a toroidal WGM microlaser.

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Optical Data Transmission with a Dissipative Kerr Soliton in an Ultrahigh-Q MgF<inf>2</inf>Microresonator

Tanaka S., Fujii S., Wada K., Kumazaki H., Kogure S., Tasaka S., Ohtsuka T., Kawanishi S., Tanabe T.

2021 Conference on Lasers and Electro-Optics Europe and European Quantum Electronics Conference, CLEO/Europe-EQEC 2021  2021.06

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Optical frequency combs based on microresonators (microcombs) have been actively researched since the first experimental achievement of soliton mode-locking. Soliton pulses (dissipative Kerr solitons; DKSs) possess high repetition rates ranging from tens to hundreds of GHz. Thanks to this feature, DKSs are expected to benefit a wide range of applications, such as optical communications. In particular, DKSs are highly suitable for wavelength division multiplexing (WDM) transmission, which exploits an individual comb line as an optical carrier, owing to its broad bandwidth and low-noise properties [1] , [2]. Although coherent transmissions are currently the mainstream of optical communication, transmissions employing the intensity-modulation direct-detection (IM-DD) method remain in use, e.g., in data centers [3]. The advantage of an IM-DD transmission is that it does not require complex digital signal processors, resulting in a low power consumption and a small-signal delay, both of which are key characteristics required in the Beyond-5G technology. The IM-DD method can be used in conjunction with microcombs to achieve high-speed transmission while maintaining these advantages.

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Stable Formation of Multiple Solitons in an Optical Microresonator Assisted by Saturable Absorption

Nakashima A., Fujii S., Imamura R., Nagashima K., Tanabe T.

2021 Conference on Lasers and Electro-Optics, CLEO 2021 - Proceedings  2021.05

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We numerically investigate soliton microcomb generation with a saturable absorption effect. We found that a cavity-integrated saturable absorber allows the formation of a much higher number of solitons than possible with a Kerr-only monolithic cavity.