2022/11/26 更新

写真a

キタ トモヒロ
北 智洋
Scopus 論文情報  
論文数: 0  Citation: 0  h-index: 12

Citation Countは当該年に発表した論文の被引用数

所属
理工学術院 先進理工学部
職名
教授

他学部・他研究科等兼任情報

  • 理工学術院   大学院先進理工学研究科

学内研究所・附属機関兼任歴

  • 2020年
    -
    2022年

    理工学術院総合研究所   兼任研究員

学位

  • 北陸先端科学技術大学院大学   工学博士(材料)

所属学協会

  •  
     
     

    日本物理学会

  •  
     
     

    電子情報通信学会

  •  
     
     

    応用物理学会

  •  
     
     

    Optical society, America

 

研究分野

  • 光工学、光量子科学

  • 電子デバイス、電子機器   半導体工学

研究キーワード

  • 非線形光学効果

  • 半導体レーザ

  • 光エレクトロニクス

  • シリコンフォトニクス

  • 半導体工学

論文

  • Demonstration of 2D beam steering using large-scale passive optical phased array enabled by multimode waveguides with reduced phase error

    Yamato Misugi, Hideaki Okayama, Tomohiro Kita

    Applied Physics Express   15 ( 10 )  2022年10月

     概要を見る

    Optical phased arrays (OPAs) have received considerable attention as solid-state beam scanners. However, conventional OPAs that actively control the phase difference between arrays are characterized by excessive power consumption for high-precision beam emission. In this study, we fabricated an OPA comprising Bragg grating and arrayed waveguide grating (AWG). Multi-mode waveguide is used in AWG to reduce the effect of manufacturing error. This device realizes wide and high-resolution two-dimensional beam steering only by sweeping wavelength. FWHM of the emitted beam is 0.534° × 2.27°, and the steering range is 43.9° × 13.5° with 1/64 of the power consumption of conventional OPA.

    DOI

    Scopus

  • High-extinction-ratio Si optical modulator loaded with integrated polarizer

    Hiroki Kojima, Junichi Fujikata, Tomohiro Kita

    Japanese Journal of Applied Physics   61 ( SK )  2022年08月

     概要を見る

    We propose a carrier-depletion type Si optical modulator for transverse electric (TE) polarization loaded with an integrated polarizer. The integrated TE-pass polarizer with a bent waveguide has a compact and simple structure and demonstrate a polarization extinction ratio of 41.3 dB and insertion loss of 0.67 dB. This Si optical modulator loaded with the integrated polarizer achieved a maximum extinction ratio of 54.5 dB. It is expected to have a wide range of applications in digital coherent optical communication and optical sensing fields.

    DOI

    Scopus

  • Microoptics

    Toshio Watanabe, Tomonari Sato, Taro Arakawa, Kiichi Hamamoto, Satoshi Iwamoto, Tomohiro Kita, Muneharu Kuwata, Shinichi Saito, Shinji Yamashita

    Japanese Journal of Applied Physics   61 ( SK )  2022年08月

    DOI

    Scopus

  • Ultrafast Silicon MZI Optical Switch with Periodic Electrodes and Integrated Heat Sink

    Tomohiro Kita, Manuel Mendez-Astudillo

    Journal of Lightwave Technology   39 ( 15 ) 5054 - 5060  2021年08月

     概要を見る

    The compact, high-speed, low-power consumption Mach-Zehnder interferometer (MZI)-type optical switch using thermo-optical effect is a key device in future optical integrated circuits. In this study, we achieved ultra-high-speed switching operation of 0.4 μs and low electrical power operation of 23 mW with a small device footprint by loading an asymmetric doped MZI structure and an integrated heat sink. This optical switch can be fabricated in the standard manufacturing process of silicon photonic devices, has high practicality and will be a useful tool in various optical integrated circuits.

    DOI

    Scopus

    2
    被引用数
    (Scopus)
  • 1.55-µm Si-Photonics-Based Heterogeneous Tunable Laser Integrated with Highly Stacked QD-RSOA

    A. Matsumoto, W. Masuda, K. Akahane, T. Umezawa, N. Yamamoto, T. Kita

    2021 Conference on Lasers and Electro-Optics, CLEO 2021 - Proceedings    2021年05月

     概要を見る

    We demonstrated a Si-photonics-based heterogeneous tunable laser in the 1.55-µm-band with quantum dot reflective semiconductor optical amplifier. Relatively low threshold current could be achieved owing to high gain characteristic.

  • C-band Tunable Dual-Wavelength Laser with a Quantum Dot SOA

    Wataru Masuda, Kissho Iwanaga, Atsushi Matsumoto, Tomohiro Kita

    Conference Digest - IEEE International Semiconductor Laser Conference    2021年

     概要を見る

    A C-band tunable dual-wavelength laser for a RoF light source is demonstrated. The difference frequency was tunable in the range of 22.6 GHz to 192.0 GHz. The generated dual-wavelength laser amplified by EDFA could be converted to a corresponding radio frequency through a high-speed photodetector.

    DOI

    Scopus

  • Narrow linewidth hybrid wavelength-tunable laser with optical negative feedback circuit

    Tatsuki Komatsubara, Toshiaki Okachi, Nobuhide Yokota, Hiroshi Yasaka, Tomohiro Kita

    IEEE International Conference on Group IV Photonics GFP   2021-December  2021年

     概要を見る

    A hybrid laser with an optical negative feedback circuit integrated on a silicon photonics chip was investigated. Our numerical analysis verified that the laser can function as a wavelength-tunable laser with a spectral linewidth of less than 10 kHz. The result was supported by experiments.

    DOI

    Scopus

  • Thermo-optic phase shifter with sub-microsecond switching time and low power consumption

    Masaki Okamoto, Manuel Mendez-Astudillo, Tomohiro Kita

    Japanese Journal of Applied Physics   59 ( SO )  2020年08月

     概要を見る

    We propose a thermo-optic phase shifter utilizing multimode interference in a silicon waveguide. The electrodes were attached to the section where the multimode interference had the minimum optical electric field around the sidewalls. We designed the multimode waveguide width to reduce optical propagation loss in the C-L wavelength band (1.53-1.625 μm). We succeeded in developing a low optical loss thermo-optic phase shifter with less than 0.1 dB in the wavelength range of 1.5 to 1.6 μm. Moreover, wavelength dependence was reduced by adjusting the number of electrodes. An optical switch with the designed thermo-optic phase shifter was fabricated and used to estimate the optical switching time. Switching time of several microseconds was obtained by normal pulse operation, and ultrafast optical switching of about 500 ns was realized by overdrive control.

    DOI

    Scopus

    1
    被引用数
    (Scopus)
  • Wavelength Tunable filter with Curved Directional Coupler

    Yoshiaki Ito, Manuel Mendez-Astudillo, Tomohiro Kita

    MOC 2019 - 24th Microoptics Conference     106 - 107  2019年11月

     概要を見る

    We investigate a structure to reduce the wavelength-dependence of a ring resonator's transmission characteristics by replacing the conventional directional coupler of the racetrack resonator with a curved directional coupler. We show its potential as a filter for broadband wavelength tunable single mode lasers

    DOI

    Scopus

  • High Speed and Low Power Consumption, Thermo-optic Phase Shifter

    Masaki Okamoto, Manuel Mendez-Astudillo, Tomohiro Kita

    MOC 2019 - 24th Microoptics Conference     144 - 145  2019年11月

     概要を見る

    We propose a thermo-optic phase shifter which uses multimode interference. Electrodes are attached to the section where the multimode interference has minimum optical power in the sidewalls. We use the Silicon large thermo-optic constant to create an integrated optical device to control the state of light in several microseconds, for both heating and cooling times.

    DOI

    Scopus

  • Athermal Silicon Ring Resonators with TiO<inf>2</inf> Hybrid-Polymer Claddings

    Tomohiro Kita, Manuel Mendez-Astudillo, Mieko Masaka, Freddy Susanto Tan, Okihiro Sugihara

    MOC 2019 - 24th Microoptics Conference     134 - 135  2019年11月

     概要を見る

    Thermo-optic coefficients of organic-inorganic hybrid polymers with rutile-TiO2 nanoparticles were carefully estimated using SOI ring resonators. Athermal operation of the SOI ring resonators with TiO2 hybrid-polymer claddings was achieved. The hybrid-polymer cladding can be applied to diverse silicon waveguide structures to control the temperature dependence of silicon photonic devices.

    DOI

    Scopus

  • Fabry-Perot Cavity Using Two Row Photonic Crystal in a Multimode Waveguide

    Manuel Mendez-Astudillo, Hideaki Okayama, Tomohiro Kita

    2019 Conference on Lasers and Electro-Optics, CLEO 2019 - Proceedings   Part F129-CLEO_SI 2019  2019年05月

     概要を見る

    We experimentally present a Fabry-Perot cavity that uses two-row photonic crystals in a multimode waveguide as the reflecting elements in an add-drop configuration to achieve fine FSR tuning and maximum footprint efficiency.

    DOI

    Scopus

    1
    被引用数
    (Scopus)
  • Camera sensor platform for high speed video data transmission using a wideband electro-optic polymer modulator

    Xiaoyang Cheng, Feng Qiu, Andrew M. Spring, Masaru Sasaki, Tsubasa Kashino, Masaaki Ozawa, Hideyuki Nawata, Tomohiro Kita, Okihiro Sugihara, Shiyoshi Yokoyama

    Optics Express   27 ( 3 ) 1877 - 1883  2019年02月

     概要を見る

    In this work, 1 GHz video data was collected by a CMOS camera and successfully transmitted by the electro-optic (EO) modulator driven by an external modulation module integrated onto the same chip. For this application, the EO modulator component included a polymer waveguide modulator, which performed a 20 GHz bandwidth, clear eye diagram opening with a Q factor of 10.3 at 32 Gbit/s and a drive voltage of 1.5 V pp . By utilizing a thermally stable EO polymer, the wide-band polymer modular can yield a photonic integrated camera sensor system which is a reliable processing platform for real-time data processing.

    DOI PubMed

    Scopus

    1
    被引用数
    (Scopus)
  • Compact thermo-optic MZI switch in silicon-on-insulator using direct carrier injection

    Manuel Mendez-Astudillo, Masaki Okamoto, Yoshiaki Ito, Tomohiro Kita

    Optics Express   27 ( 2 ) 899 - 906  2019年01月

     概要を見る

    In this paper we present a compact direct current injection thermo-optic switch based on a Mach-Zehnder Interferometer configuration that is suitable for autonomous vehicle applications as it has a low heating resistance value of 97 Ω, a rapid 2.16 μs switching time constant, and a Pπ of 28 mW. The device relies on multimode interference to achieve low optical insertion losses of less than 1.1 dB per device, while allowing direct current injection to heat the waveguide and achieve fast operation speeds. Furthermore, the total resistive value can be tailored as the heating elements are placed in parallel.

    DOI PubMed

    Scopus

    20
    被引用数
    (Scopus)
  • Rectangular resonators on silicon-on-insulator with large sensing area for object detection

    Manuel Mendez-Astudillo, Hideaki Okayama, Hirochika Nakajima, Tomohiro Kita

    Japanese Journal of Applied Physics   58 ( SJ )  2019年

     概要を見る

    In this paper we experimentally demonstrate the possibility of detecting an object using a rectangular resonator with a surface area of 200 μm2. The optical biosensor is fabricated on the standard silicon-on-insulator platform, and the object is sensed with the evanescent field that extends from the top of the device. It is possible to detect the presence of the object by measuring the shift of the resonant wavelengths in the transmission spectrum. We compare the performance of the device when it is operated in TE and TM polarization, obtaining superior performance with TM polarization, whereby it achieves a shift of 1.5 nm when a large element is placed on its surface.

    DOI

    Scopus

    1
    被引用数
    (Scopus)
  • Compact narrow-linewidth optical negative feedback laser with Si optical filter

    Aoyama Konosuke, Kobayashi Shuhei, Wada Masashi, Yokota Nobuhide, Kita Tomohiro, Yasaka Hiroshi

    APPLIED PHYSICS EXPRESS   11 ( 11 )  2018年11月  [査読有り]

    DOI

    Scopus

    5
    被引用数
    (Scopus)
  • Phase-Shifted Multimode Bragg Gratings in Silicon-on-Insulator for Sensing Applications

    Manuel Mendez-Astudillo, Hideaki Okayama, Tomohiro Kita, Hirochika Nakajima

    IEEE International Conference on Group IV Photonics GFP   2018-August   49 - 50  2018年10月

     概要を見る

    In this paper, we experimentally characterize the sensitivity of different types of multimode Bragg gratings in Silicon-On-Insulator and demonstrate a high sensitivity of 120 nm per refractive index unit using Bragg gratings for TM polarized light.

    DOI

    Scopus

    1
    被引用数
    (Scopus)
  • Two-Wavelength Tunable Laser Diode using a Quantum Dot SOA and a Silicon Photonic External Cavity

    Tomohiro Kita, Atsushi Matsumoto, Naokatsu Yamamoto, Manuel Mendez-Astudillo, Hirohito Yamada

    2018 IEEE International Semiconductor Laser Conference (ISLC)   2018-September   23 - 24  2018年09月

     概要を見る

    We propose a tunable two-wavelength heterogeneous quantum dot laser diode. The tunable two-wavelength laser consists of a quantum dot semiconductor optical amplifier and an external cavity fabricated from silicon photonics technology as the two-wavelength tunable filter. We successfully demonstrated two-wavelength lasing oscillation by tuning the difference frequency from approximately 34 GHz to 400 GHz.

    DOI

  • Tunable Dual-Wavelength Heterogeneous Quantum Dot Laser Diode with a Silicon External Cavity

    Tomohiro Kita, Atsushi Matsumoto, Naokatsu Yamamoto, Hirohito Yamada

    Journal of Lightwave Technology   36 ( 2 ) 219 - 224  2018年01月  [査読有り]  [招待有り]

     概要を見る

    We propose a tunable dual-wavelength heterogeneous quantum dot laser diode. The tunable dual-wavelength laser consists of a quantum dot semiconductor optical amplifier as the optical gain medium and an external cavity fabricated from silicon photonics technology as the wavelength tunable filter. We successfully demonstrated dual-wavelength lasing oscillation by tuning the difference frequency from approximately 34 to 400 GHz.

    DOI

    Scopus

    11
    被引用数
    (Scopus)
  • Narrow Spectral Linewidth Silicon Photonic Wavelength Tunable Laser Diode for Digital Coherent Communication System

    Tomohiro Kita, Rui Tang, Hirohito Yamada

    IEEE JOURNAL OF SELECTED TOPICS IN QUANTUM ELECTRONICS   22 ( 6 ) 23 - 34  2016年11月  [査読有り]  [招待有り]

     概要を見る

    We demonstrated wavelength tunable laser diodes with Si-wire waveguide ring resonators as an external optical cavity. The footprint of the optical cavity including the semiconductor optical amplifier is as small as 0.8 mm x 0.6 mm which is less 1/10 of those made of silicon oxinitride material. Wavelength tuning range of approximately 55 nm was demonstrated, which covers entire L-band of the optical communication wavelength system. Furthermore, a spectral linewidth narrower than 100 kHz was obtained by optimizing the design of the external optical cavity. The optical nonlinearity of silicon is described and the influence on laser oscillation is also discussed.

    DOI

    Scopus

    31
    被引用数
    (Scopus)
  • Heterogeneous quantum dot/silicon photonics-based wavelength-tunable laser diode with a 44 nm wavelength-tuning range

    Tomohiro Kita, Naokatsu Yamamoto, Atsushi Matsumoto, Tetsuya Kawanishi, Hirohito Yamada

    JAPANESE JOURNAL OF APPLIED PHYSICS   55 ( 4 ) 04EH11-1 - 04EH11-4  2016年04月  [査読有り]

     概要を見る

    A heterogeneous wavelength-tunable laser diode combining quantum dot and silicon photonics technologies is proposed. A compact wavelength-tunable filter with two ring resonators was carefully designed and fabricated using silicon photonics technology. The tunable laser combining the wavelength-tunable filter and an optical amplifier, which includes InAs quantum dots, achieved a 44.0 nm wavelength-tuning range at around 1250 nm. The broadband optical gain of the quantum dot optical amplifier was effectively used by the optimized wavelength-tunable filter. This heterogeneous wavelength-tunable laser diode could become a breakthrough technology for high-capacity data transmission systems. (C) 2016 The Japan Society of Applied Physics

    DOI

    Scopus

    17
    被引用数
    (Scopus)
  • Instability of Silicon Photonic Wavelength Tunable Laser Diodes due to the Nonlinear Optical Effect of Silicon

    Tomohiro Kita, Hirohito Yamada

    2016 INTERNATIONAL SEMICONDUCTOR LASER CONFERENCE (ISLC)    2016年  [査読有り]

     概要を見る

    The silicon photonic wavelength tunable laser diode is a good candidate for the integrated light source of the digital coherent optical communication system. However, optical nonlinear effects easily occur due to the strong light confinement of Si photonic wire waveguides. The impact on laser operation caused by nonlinearity was discussed.

  • Quantum dots and silicon photonics combine in broadband tunable laser

    Tomohiro Kita, Naokatsu Yamamoto

    LASER FOCUS WORLD   51 ( 11 ) 45 - 48  2015年11月  [査読有り]

     概要を見る

    A new wavelength-tunable laser diode combines quantum-dot (QD) technology and silicon photonics with large optical gains around the 1310 nm telecom window and is amenable to integration of other passive and active components towards a truly integrated photonic platform.

  • Ultra-compact wavelength-tunable quantum-dot laser with silicon-photonics double ring filter

    Tomohiro Kita, Naokatsu Yamamoto, Tetsuya Kawanishi, Hirohito Yamada

    APPLIED PHYSICS EXPRESS   8 ( 6 ) 062701 - 062704  2015年06月  [査読有り]

     概要を見る

    Compact, wavelength-tunable light sources are desired for the enhancement of information communication technology and bio-imaging applications. We propose a compact, wavelength-tunable laser diode with a wide wavelength-tunable range around 1230 nm consisting of a quantum-dot optical amplifier and a silicon photonic tunable filter. High-quality InAs quantum dots grown with the sandwiched sub-nano separator technique were used as the optical gain medium. The wavelength-tunable filter was constructed with ring resonators fabricated using silicon photonics. The single-mode laser oscillation was demonstrated with a 28.5-nm wavelength-tunable range. (C) 2015 The Japan Society of Applied Physics

    DOI

    Scopus

    22
    被引用数
    (Scopus)
  • Optimum waveguide-core size for reducing device property distribution of Si-wire waveguide devices

    Munetoshi Soma, Tomohiro Kita, Yuichiro Tanushi, Munehiro Toyama, Miyoshi Seki, Nobuyuki Yokoyama, Minoru Ohtsuka, Hirohito Yamada

    JAPANESE JOURNAL OF APPLIED PHYSICS   54 ( 4 ) 04DG03  2015年04月  [査読有り]

     概要を見る

    We investigated the waveguide-core size distribution of ring resonators fabricated on a 300mm silicon-on-insulator (SOI) wafer using a CMOS-compatible process featuring ArF immersion lithography. These ring resonators were constructed in a Si-wire waveguide with a standard core size of 400nm width and 220nm height. The group refractive indices of the waveguide were derived from the transmission spectra of the ring resonators. From the deviation of these group refractive indices, the waveguide-core width distribution was estimated to be 5 nm, and the waveguide-core height distribution was estimated to be 1 nm. Moreover, the device property distribution of various Si-wire waveguide depended on the estimated fabrication error was calculated. The waveguide core with the smallest device property distribution had a 540nm width and a 160nm height, and this waveguide has a device property distribution of 2/3 value compared with the standard core size. (C) 2015 The Japan Society of Applied Physics

    DOI

    Scopus

    4
    被引用数
    (Scopus)
  • Narrow-spectral-linewidth silicon photonic wavelength-tunable laser with highly asymmetric Mach-Zehnder interferometer

    Rui Tang, Tomohiro Kita, Hirohito Yamada

    OPTICS LETTERS   40 ( 7 ) 1504 - 1507  2015年04月  [査読有り]

     概要を見る

    We propose a narrow-spectral-linewidth silicon photonic wavelength-tunable laser with a novel external wavelength-tunable filter, which consists of two silicon ring resonators with different circumferences and a highly asymmetric Mach-Zehnder interferometer (MZI), the two optical paths of which have significantly different lengths. Calculations and experimental results indicated that the gain difference between longitudinal modes was increased by the highly asymmetric MZI. Consequently, a narrow spectral linewidth of 12 kHz and a stable single-mode oscillation were obtained. (C) 2015 Optical Society of America

    DOI

    Scopus

    18
    被引用数
    (Scopus)
  • Silicon Photonic Hybrid Ring-Filter External Cavity Wavelength Tunable Lasers

    Naoki Kobayashi, Kenji Sato, Masahiko Namiwaka, Keisuke Yamamoto, Shinya Watanabe, Tomohiro Kita, Hirohito Yamada, Hiroyuki Yamazaki

    JOURNAL OF LIGHTWAVE TECHNOLOGY   33 ( 6 ) 1241 - 1246  2015年03月  [査読有り]

     概要を見る

    Si-photonic hybrid ring external cavity wavelength tunable lasers by passive alignment techniques with more than 100-mW fiber-coupled power and linewidth narrower than 15 kHz along the whole C-band are demonstrated. These attractive performances are achieved due to very low loss Si-wire waveguides, of which loss is lower than 0.5 dB/cm. Obtained results show excellent features of Si-photonics toward commercial products.

    DOI

    Scopus

    127
    被引用数
    (Scopus)
  • Compact silicon photonic wavelength-tunable laser diode with ultra-wide wavelength tuning range

    Tomohiro Kita, Rui Tang, Hirohito Yamada

    APPLIED PHYSICS LETTERS   106 ( 11 ) 111104  2015年03月  [査読有り]

     概要を見る

    We present a wavelength-tunable laser diode with a 99-nm-wide wavelength tuning range. It has a compact wavelength-tunable filter with high wavelength selectivity fabricated using silicon photonics technology. The silicon photonic wavelength-tunable filter with wide wavelength tuning range was realized using two ring resonators and an asymmetric Mach-Zehnder interferometer. The wavelength-tunable laser diode fabricated by butt-joining a silicon photonic filter and semiconductor optical amplifier shows stable single-mode operation over a wide wavelength range. (C) 2015 AIP Publishing LLC.

    DOI

    Scopus

    25
    被引用数
    (Scopus)
  • Silicon Photonic Wavelength-Tunable Laser Diode With Asymmetric Mach-Zehnder Interferometer

    Tomohiro Kita, Keita Nemoto, Hirohito Yamada

    IEEE JOURNAL OF SELECTED TOPICS IN QUANTUM ELECTRONICS   20 ( 4 ) 8201806_1 - 8201806_6  2014年07月  [査読有り]

     概要を見る

    We fabricated wavelength-tunable laser diodes using a Si photonic wavelength filer that consists of ring resonators and an asymmetric Mach-Zehnder interferometer. The footprint of the optical cavity including the semiconductor optical amplifier is small, 2.6 mm x 0.5 mm, which is about 1/9 of those for tunable laser diodes made of silicon oxynitride. The wavelength could be tuned over approximately 62 nm, which covers the entire L-band of the optical communication wavelength range. The maximum output power reaches 42.2mW. Furthermore, a spectral line width narrower than 100 kHz was obtained. Such tunable laser diodes with narrow spectral line widths are suitable as light sources integrated into other digital coherent devices.

    DOI

    Scopus

    33
    被引用数
    (Scopus)
  • Long external cavity Si photonic wavelength tunable laser diode

    Tomohiro Kita, Keita Nemoto, Hirohito Yamada

    JAPANESE JOURNAL OF APPLIED PHYSICS   53 ( 4 ) 04EG04_1 - 04EG04_4  2014年04月  [査読有り]

     概要を見る

    We fabricated wavelength-tunable laser diodes with external cavity consist of Si photonic wire waveguide ring resonators. About 51.5 nm wavelength tuning operation, which covers the entire L-band of the optical communication wavelength range, was obtained. The cavity length dependence of the spectral line width was verified to obtain narrower spectral linewidth. The observed spectral linewidth of 3.78 mm long cavity and 8.19 mm long cavity are 131.0 and 64.8 kHz, respectively. The advantage of long external cavity to design the narrow spectral linewidth Si photonic wavelength tunable laser diode was confirmed. (C) 2014 The Japan Society of Applied Physics

    DOI

    Scopus

    20
    被引用数
    (Scopus)
  • Wide-band Wavelength Tunable Laser Diode with Si Photonic Filter

    Tomohiro Kita, Rui Tang, Hirohito Yamada

    2014 24TH IEEE INTERNATIONAL SEMICONDUCTOR LASER CONFERENCE (ISLC 2014)     149 - 150  2014年  [査読有り]

     概要を見る

    We investigated the wide-band wavelength tuning operation to increase the possibility of silicon photonic wavelength tunable laser diodes which is composed semiconductor optical amplifier and silicon photonic waveguide filter. The wide-band wavelength tuning operation of 94.1 nm was demonstrated.

    DOI

  • High Output Power and Narrow Linewidth Silicon Photonic Hybrid Ring-Filter External Cavity Wavelength Tunable Lasers

    K. Sato, N. Kobayashi, M. Namiwaka, K. Yamamoto, T. Kita, H. Yamada, H. Yamazaki

    2014 EUROPEAN CONFERENCE ON OPTICAL COMMUNICATION (ECOC)   33   1241 - 1244  2014年  [査読有り]  [招待有り]

     概要を見る

    Si-photonic Hybrid Ring-filter External Cavity (SHREC) wavelength tunable lasers by passive alignment techniques with over 100-mW fiber-coupled power and linewidth narrower than 15 kHz along the whole C-band are demonstrated. Obtained results show excellent features of Si-photonics towards commercial products.

    DOI

    Scopus

    127
    被引用数
    (Scopus)
  • Highly-stabilized operation of Si photonics wavelength tunable laser diode

    Tomohiro Kita, Keita Nemoto, Hirohito Yamada

    Extended abstract of Solid State Device and Materials    2013年09月  [査読有り]

  • Nonlinear optical photonic crystal waveguide with TiO2 material

    Koji Uchijima, Tomohiro Kita, Hirohito Yamada

    OXIDE-BASED MATERIALS AND DEVICES IV   8626  2013年

     概要を見る

    Titanium dioxide (TiO2) has several attractive properties such as high linear and nonlinear refractive indices and the wide bandgap for applying the nonlinear optical devices. We have been studied channel waveguides with TiO2 as the submicron size core to verify their feasibility as the nonlinear optical devices. In this study, we analyzed optical propagation in the TiO2 photonic crystal waveguide and demonstrated the enhanced optical nonlinearity due to slow light effect.

    DOI

    Scopus

    1
    被引用数
    (Scopus)
  • Anomalous localization modes in Bragg-grating based on high index-difference waveguide

    Tomohiro Kita, Koji Uchijima, Hirohito Yamada

    SILICON PHOTONICS VIII   8629  2013年

     概要を見る

    We observed photonic band-gap disappearance on Bragg-grating wavelength filters with Si photonic-wire waveguides, and studied the physical mechanism with theoretical and numerical analyses. This is a unique phenomenon observed in channel waveguides with very high index-contrast between the waveguide core and cladding materials. The photonic band-gap disappearance was observed in structures where two different optical field distributions of standing wave degenerate.

    DOI

    Scopus

  • Narrow-Spectral-Linewidth Wavelength-Tunable Laser Diode with Si Wire Waveguide Ring Resonators

    Keita Nemoto, Tomohiro Kita, Hirohito Yamada

    APPLIED PHYSICS EXPRESS   5 ( 8 ) 082701-1 - 082701-3  2012年08月  [査読有り]

     概要を見る

    We fabricated wavelength-tunable laser diodes with Si wire waveguide ring resonators as an external optical cavity. The footprint of the optical cavity including the semiconductor optical amplifier is as small as 2.73 x 0.89 mm(2), which is about 1/5 of those made of silicon oxinitride material. About 44-nm-wavelength tuning operation, which covers the entire L-band of the optical communication wavelength range, was obtained. Furthermore, spectral linewidth narrower than 100 kHz was obtained by optimizing the design of the external optical cavity. The tunable laser diodes with narrow spectral linewidth are suitable as light sources for digital coherent optical transmission systems. (C) 2012 The Japan Society of Applied Physics

    DOI

    Scopus

    42
    被引用数
    (Scopus)
  • Analysis of Phase Matching Conditions for Generating Second Harmonic in ZnO Channel Waveguides

    Yuta Taira, Tomohiro Kita, Edgar Yoshio Morales Teraoka, Hirohito Yamada

    JAPANESE JOURNAL OF APPLIED PHYSICS   51 ( 4 ) 04DG04-1 - 04DG04-4  2012年04月  [査読有り]

     概要を見る

    We describe a phase-matching scheme for generating the second harmonic in ZnO channel waveguides using a modal phase-matching (MPM) method. We found that MPM can be achieved between the TM00 mode of the fundamental wave and the TM02 mode of the second-harmonic wave by using structural dispersion of the waveguide mode. Furthermore, we calculated the normalized conversion efficiency by taking the overlap integral of each waveguide mode and the effective area of the fundamental wave into account, and obtained a sufficiently high conversion efficiency. These results show that ZnO channel waveguides are very attractive for generating second-harmonic devices. (C) 2012 The Japan Society of Applied Physics

    DOI

    Scopus

    2
    被引用数
    (Scopus)
  • Theoretical analysis of vertical coupling optical I/O interface with reflectors

    奈良 匡樹, 北 智洋, 田主 裕一朗, 山田 博仁

    電気関係学会東北支部連合大会講演論文集   2012   16 - 16  2012年

    DOI CiNii

  • TiO2 photonic crystal waveguide for nonlinear optical applications

    内島 晃司, 北 智洋, 山田 博仁

    電気関係学会東北支部連合大会講演論文集   2012   18 - 18  2012年

    DOI CiNii

  • Analysis of the Nonlinear Optical Parameter of ZnO Channel Waveguides

    Edgar Yoshio Morales Teraoka, Tomohiro Kita, Daniel H. Broaddus, Atsushi Tsukazaki, Masashi Kawasaki, Alexander L. Gaeta, Hirohito Yamada

    JAPANESE JOURNAL OF APPLIED PHYSICS   50 ( 4 ) 04DG01  2011年04月  [査読有り]

     概要を見る

    In this paper, we analyze the nonlinear optical parameter gamma estimated from experimental results of spectral broadening in ZnO channel waveguides. The effective area was calculated for waveguides of various dimensions and using the resulting data, the nonlinear optical parameter gamma was obtained analytically. We compare these values with those estimated from measurements, and found good agreement between them. We extended the analysis to calculate the optimal size for maximum nonlinearity and found that the fabricated waveguides were very close to the optimal size. (C) 2011 The Japan Society of Applied Physics

    DOI

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    2
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  • Optical Crossing and Integration Using Hybrid Si-Wire/Silica Waveguides

    Younosuke Wakayama, Tomohiro Kita, Hirohito Yamada

    JAPANESE JOURNAL OF APPLIED PHYSICS   50 ( 4 ) 04DG20  2011年04月  [査読有り]

     概要を見る

    We studied the feasibility of an integrated optical circuit consisting of Si-wire waveguides and silica-based waveguides. In order to realize such a hybrid waveguide optical circuit, we investigated a waveguide junction structure based on adiabatic mode conversion with tapered Si and a waveguide crossing structure of heterogeneous waveguides by numerical analysis and measurements. We estimated the optical coupling loss between the waveguides to be 0.39 dB from the measurements. We also estimated the insertion loss of the waveguide crossing to be less than 0.7 dB, and the crosstalk between the waveguides to be less than -35 dB by numerical analysis. (C) 2011 The Japan Society of Applied Physics

    DOI

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    7
    被引用数
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  • Variation of optical properties by the crystalline phase transition of polycrystalline silicon

    Hidenori Iwata, Tomohiro Kita, Hirohito Yamada

    SILICON PHOTONICS VI   7943   50  2011年

     概要を見る

    We studied a characteristics trimming technique in Si photonic-wire waveguide devices. In order to trimming device properties, we utilized refractive index change of amorphous silicon when it crystallizes by annealing. We fabricated MZI devices with amorphous silicon waveguides, and demonstrated the trimming of the transmission spectra by thermal annealing and also laser annealing after finished the device fabrication process. We observed 5.2 % of the refractive index change owing to crystallization by annealing in a nitrogen atmosphere and 5.8% of change by laser crystallization.

    DOI

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  • Wavelength Tunable Laser Diodes with Si-Wire Waveguide Ring Resonator Wavelength Filters

    Ken Suzuki, Tomohiro Kita, Hirohito Yamada

    SILICON PHOTONICS VI   7943   51  2011年

     概要を見る

    We fabricated wavelength tunable laser diodes consisting of ring resonator wavelength filters with Si-wire waveguides. More than 45 nm wavelength tuning operation was obtained by about 100 mW heating power. We also measured spectral linewidth of the tunable laser, and observed about 200 kHz of spectral linewidth.

    DOI

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    12
    被引用数
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  • Nonlinear optical waveguides with rutile TiO(2)

    Koichi Abe, Edgar Yoshio Morales Teraoka, Tomohiro Kita, Hirohito Yamada

    OXIDE-BASED MATERIALS AND DEVICES II   7940 ( 49 )  2011年

     概要を見る

    We investigated a possibility of making rutile TiO(2) channel waveguides for nonlinear optical applications. Single mode conditions, the group velocity dispersion and the nonlinear-optical parameters for the rutile TiO(2) channel waveguides were calculated using the finite-element method. We also fabricate channel waveguides with rutile TiO(2) using reactive ion etching. The propagation loss measured by the cut-back method was around 6 dB/mm. According to our simulation, around 70 nm of spectral broadening owing to the self-phase modulation will be expected by a pumping optical pulse with 360 W peak power.

    DOI

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    6
    被引用数
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  • Fabrication of ZnO channel waveguides for nonlinear optical applications

    Edgar Yoshio Morales Teraoka, Tomohiro Kita, Atsushi Tsukazaki, Masashi Kawasaki, Hirohito Yamada

    OXIDE-BASED MATERIALS AND DEVICES II   7940 ( 48 )  2011年

     概要を見る

    We present a fabrication procedure for ZnO channel waveguides intended for nonlinear optical applications. Ar ion milling was used to etch the single crystal thin film samples, and the effects of bias power, chamber pressure and Ar flow rate were investigated, finding optimal parameters for waveguide fabrication. The effect of sidewall roughness was estimated by comparing the results of cut-back measurements and an analytical model. We show an easy and effective method for the fabrication of ZnO channel waveguides.

    DOI

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    1
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  • Self-phase modulation at visible wavelengths in nonlinear ZnO channel waveguides

    Edgar Yoshio Morales Teraoka, Daniel H. Broaddus, Tomohiro Kita, Atsushi Tsukazaki, Masashi Kawasaki, Alexander L. Gaeta, Hirohito Yamada

    APPLIED PHYSICS LETTERS   97 ( 7 ) 71105 - 71107  2010年08月  [査読有り]

     概要を見る

    We report the observation of nonlinear optical effects in the visible spectrum using ZnO channel waveguides. We demonstrate sixfold spectral broadening and a 2 pi phase shift due to self-phase modulation in ZnO channel waveguides using femtosecond optical pulses with a center wavelength of 840 nm. We measured a value for the nonlinear parameter gamma of 13.9 +/- 3.0 W-1 m(-1), which is more than 1300 times that of a highly nonlinear fiber. The calculated intensity-dependent refractive index is found to be consistent with previously reported values of bulk single-crystal ZnO. (C) 2010 American Institute of Physics. [doi: 10.1063/1.3480422]

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    20
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  • Experimental and numerical analysis study of 1-D photonic crystal in Si photonic-wire waveguides

    Tomohiro Kita, Hirohito Yamada

    SILICON PHOTONICS V   7606  2010年

     概要を見る

    We have systematically studied Bragg Grating Filters in Si photonic-wire waveguides. Highly uniform samples have been fabricated in a specialized foundry service for Si photonics. The reflected wavelength has been controlled over an 180 nm range. By changing the design parameters we controlled the photonic band-gap to be between 6 to 16 nm. Thermal tuning of the reflected wavelength was also measured, resulting in a wavelength shift of more than 3 nm.

    DOI

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  • ZnO Channel Waveguides for Nonlinear Optical Applications

    Edgar Yoshio Morales Teraoka, Tomohiro Kita, Atsushi Tsukazaki, Masashi Kawasaki, Yasuo Ohtera, Hirohito Yamada

    JAPANESE JOURNAL OF APPLIED PHYSICS   49 ( 4 ) 04DG15-1 - 04DG15-4  2010年  [査読有り]

     概要を見る

    ZnO channel waveguides were fabricated for the first time, for the purpose of being used in nonlinear optical applications. Wide-bandgap ZnO was chosen for the core material to avoid two-photon absorption at wavelengths above 800nm which are used for biomedical applications. We calculated the single-mode conditions and group-velocity dispersion of the propagating modes for the waveguides. We also fabricated channel waveguides using single-crystal ZnO thin film grown on sapphire substrate. Measured propagation losses with a cut-back method were approximately 3 to 6 dB/mm for single-mode waveguides. (C) 2010 The Japan Society of Applied Physics

    DOI

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    9
    被引用数
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  • ZnO 非線形光学効果光導波路

    モラレス 芳男, 北 智洋, 塚崎 敦, 川崎 雅司, 大寺 康夫, 山田 博仁

    電子情報通信学会 信学技報   OPE2008 ( 143 ) 35 - 40  2008年12月

  • Fabrication of a few-electron In0.56Ga0.44As vertical quantum dot with an Al2O3 gate insulator

    T. Kita, D. Chiba, Y. Ohno, H. Ohno

    PHYSICA E-LOW-DIMENSIONAL SYSTEMS & NANOSTRUCTURES   40 ( 6 ) 1930 - 1932  2008年04月  [査読有り]

     概要を見る

    For the study of spin-dependent transport in narrow-gap semiconductor nanostructures, we fabricated a few-electron quantum dot based on an In0.56Ga0.44As resonant tunneling diode structure with an Al2O3 gate insulator formed by atomic layer deposition and an air-bridge drain electrode. This gated quantum dot device allows us to control the number of electrons from zero to a few dozen without leakage problem. We describe the processing techniques and the characteristics of the low-temperature transport. (C) 2007 Elsevier B.V. All rights reserved.

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  • Fine structure in magnetospectrum of vertical quantum dot

    Oleksiy B. Agafonov, Tomohiro Kita, Hideo Ohno, Rolf J. Haug

    PHYSICA E-LOW-DIMENSIONAL SYSTEMS & NANOSTRUCTURES   40 ( 5 ) 1630 - 1632  2008年03月  [査読有り]

     概要を見る

    The electronic transport properties of a gated vertical quantum dot fabricated of an asymmetrical InGaAs/AlGaAs double-barrier resonant tunneling heterostructure are studied experimentally. At a temperature of 15 mK, a series of small current peaks are observed far below the voltage of a main resonance peak. The voltage position of these peaks appeared to be strongly dependent on the presence of magnetic field oriented perpendicular to the plane of the barriers. The occurrence of the peaks is attributed to tunneling mechanisms involving inter- Landau- level resonant tunneling, longitudinal-optical (LO)-phonon-assisted tunneling and to electrostatic effects such as Coulomb blockade (C) 2007 Elsevier B.V. All rights reserved.

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  • Effect of vertical electric fields on exciton fine structure of GaAs natural quantum dots

    S. Marcet, T. Kita, K. Ohtani, H. Ohno

    PHYSICA E   40   2069  2008年  [査読有り]

    DOI

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    3
    被引用数
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  • A few-electron vertical In0.56Ga0.44As quantum dot with an insulating gate

    T. Kita, D. Chiba, Y. Ohno, H. Ohno

    APPLIED PHYSICS LETTERS   91 ( 23 ) 232101  2007年12月  [査読有り]

     概要を見る

    Using an Al2O3 gate insulator by atomic layer deposition and air-bridge drain electrode, we fabricated a quantum dot with few electrons based on an In0.56Ga0.44As resonant tunneling diode structure. Artificial atomic properties manifested themselves in magnetotransport, enabling the determination of effective electron g factors. Results show that the insulating gate structure used here is effective for realizing quantum dots made of narrow-gap semiconductors for studying spin-related phenomena. (c) 2007 American Institute of Physics.

    DOI

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    1
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  • Combinatorial synthesis and high throughput evaluation of thermoelectric power factor in Mg-Si-Ge ternary compounds

    M. Watanabe, T. Kita, T. Fukumura, A. Ohtomo, K. Ueno, M. Kawasaki

    APPLIED SURFACE SCIENCE   254 ( 3 ) 777 - 780  2007年11月  [査読有り]

     概要を見る

    Discrete phase libraries of thermoelectric compounds, Mg(x)Si(y)Ge(1-y), were fabricated by a combinatorial pulsed laser deposition followed by annealing as a thin film form on an integrated ceramic substrate. In the substrate are embedded four probe electrical contacts to each sample, lead wires and pads to be accessed by needle probes. Resistivity and Seebeck coefficient were evaluated electrically, while temperature difference was locally given to each sample by a local heater also embedded in the substrate. The sample temperature (300-673 K) was controlled by a heating stage and temperature difference at the two contact points for each sample was evaluated by an infrared camera. The dependences of polarity and absolute values of Seebeck coefficient on the composition agree well with the data in literature. (C) 2007 Elsevier B.V. All rights reserved.

    DOI

  • Quantum Hall effect in polar oxide heterostructures

    A. Tsukazaki, A. Ohtomo, T. Kita, Y. Ohno, H. Ohno, M. Kawasaki

    SCIENCE   315 ( 5817 ) 1388 - 1391  2007年03月  [査読有り]

     概要を見る

    We observed Shubnikov-de Haas oscillation and the quantum Hall effect in a high-mobility two-dimensional electron gas in polar ZnO/Mg(x)Zn(1-x)O heterostructures grown by laser molecular beam epitaxy. The electron density could be controlled in a range of 0.7 x 10(12) to 3.7 x 10(12) per square centimeter by tuning the magnesium content in the barriers and the growth polarity. From the temperature dependence of the oscillation amplitude, the effective mass of the two-dimensional electrons was derived as 0.32 +/- 0.03 times the free electron mass. Demonstration of the quantum Hall effect in an oxide heterostructure presents the possibility of combining quantum Hall physics with the versatile functionality of metal oxides in complex heterostructures.

    DOI

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    517
    被引用数
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  • (In,Ga)As gated-vertical quantum dot with an Al2O3 insulator

    T. Kita, D. Chiba, Y. Ohno, H. Ohno

    APPLIED PHYSICS LETTERS   90 ( 6 ) 062102  2007年02月  [査読有り]

     概要を見る

    The authors fabricated a gated-vertical (In,Ga)As quantum dot with an Al2O3 gate insulator deposited using atomic layer deposition and investigated its electrical transport properties at low temperatures. The gate voltage dependence of the dI/dV-V characteristics shows clear Coulomb diamonds at 1.1 K. The metal-insulator gate structure allowed the authors to control the number of electrons in the quantum dot from 0 to a large number estimated to be about 130. (c) 2007 American Institute of Physics.

    DOI

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    7
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  • Bias voltage dependence of the electron spin injection studied in a three-terminal device based on a (Ga,Mn)As/n(+)-GaAs Esaki diode

    M. Kohda, T. Kita, Y. Ohno, F. Matsukura, H. Ohno

    APPLIED PHYSICS LETTERS   89 ( 1 ) 012103 - 012105  2006年07月  [査読有り]

     概要を見る

    We investigated injection of spin polarized electrons in a (Ga,Mn)As/n(+)-GaAs Esaki diode (ED) by using a three-terminal device integrating a (Ga,Mn)As ED and a light emitting diode (LED). Electroluminescence polarization (P-EL) from the LED was measured under the Faraday configuration as a function of bias voltages applied independently to the Esaki diode and to the LED. The maximum P-EL of 32.4% was observed when the valence electrons near the Fermi energy of (Ga,Mn)As are ballistically injected into the LED. (c) 2006 American Institute of Physics.

    DOI

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    37
    被引用数
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  • Pulse-width and magnetic-field dependences of current-induced magnetization switching in a (Ga,Mn)As magnetic tunnel junction

    D Chiba, T Kita, F Matsukura, H Ohno

    JOURNAL OF APPLIED PHYSICS   99 ( 8 ) 08G514  2006年04月  [査読有り]

     概要を見る

    We have investigated the pulse-width and magnetic-field dependences of current-induced magnetization switching in a (Ga,Mn)As/GaAs/(Ga,Mn)As magnetic tunnel junction. Critical current to induce magnetization switching shows a linear dependence on pulse width from 10 to 1000 mu s. The magnetic-field dependence appears to indicate that the observed current-induced magnetization switching proceeds through metastable magnetization structures. (C) 2006 American Institute of Physics.

    DOI

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    7
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  • Spin injection with three terminal device based on (Ga,Mn)As/n(+)-GaAs tunnel junction

    T. Kita, M. Kohda, Y. Ohno, F. Matsukura, H. Ohno

    PHYSICA STATUS SOLIDI C - CURRENT TOPICS IN SOLID STATE PHYSICS, VOL 3, NO 12   3 ( 12 ) 4164 - 4167  2006年  [査読有り]

     概要を見る

    We have fabricated a three terminal device integrating a (Ga,Mn)As Esaki diode and a light emitting diode (LED) to investigate the bias-voltage dependence of the injection of spin polarized electrons. The electroluminescence polarization (P-EL) from the LED was measured under Faraday configuration as a function of bias voltages applied independently to the Esaki diode and to the LED. The polarization shows strong dependence on the bias applied to the Esaki diode when the LED bias is fixed. The maximum P-EL of 32.4% was observed when the valence electrons near the Fermi energy of (Ga,Mn)As are injected into the LED. (c) 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

    DOI

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    5
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  • Spin-polarized transport in adiabatic quantum point contact with strong Rashba spin–orbit interaction

    T. Kita, T. Kakegawa, M. Akabori, S. Yamada

    SOLID STATE COMMUNICATIONS   136 ( 8 ) 479 - 483  2005年11月  [査読有り]

    DOI

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    1
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  • Current-driven magnetization reversal in a ferromagnetic semiconductor (Ga,Mn)As/GaAs/(Ga,Mn)As tunnel junction

    D Chiba, Y Sato, T Kita, F Matsukura, H Ohno

    PHYSICAL REVIEW LETTERS   93 ( 21 ) 216602 - 216605  2004年11月  [査読有り]

     概要を見る

    Current-driven magnetization reversal in a ferromagnetic semiconductor based (Ga,Mn)As/GaAs/(Ga,Mn)As magnetic tunnel junction is demonstrated at 30 K. Magnetoresistance measurements combined with current pulse application on a rectangular 1.5x0.3 mum(2) device revealed that magnetization switching occurs at low critical current densities of 1.1-2.2x10(5) A/cm(2) despite the presence of spin-orbit interaction in the p-type semiconductor system. Possible mechanisms responsible for the effect are discussed.

    DOI

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    145
    被引用数
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  • Nonmagnetic impurity effects in MgB2

    K Watanabe, T Kita

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   73 ( 8 ) 2239 - 2244  2004年08月  [査読有り]

     概要を見る

    We study nonmagnetic impurity effects in MgB2 using the quasiclassical equations of superconductivity for a weak-coupling two-band model. Parameters in the model are fixed so as to reproduce experiments on MgB2 as closely as possible. The quasiparticle density of states and the specific heat are calculated for various values of the interband impurity scattering. The density of states changes gradually from a two-gap structure into the conventional single-gap structure as the interband scattering increases. It is found that the excitation threshold is not a monotonic function of the interband scattering. Calculated results for the specific heat are in good agreements with experiments on samples after irradiation.

    DOI

  • Spin-polarized transport in Rashba quantum point contacts

    T Kita, T Kakegawa, M Akabori, S Yamada

    PHYSICA E-LOW-DIMENSIONAL SYSTEMS & NANOSTRUCTURES   22 ( 1-3 ) 464 - 467  2004年04月  [査読有り]

     概要を見る

    Two types of quantum point contacts (QPCs), side-gate quantum wire and split-gate QPCs, were fabricated at high In-content InGaAs/InAlAs single heterojunction which confines two-dimensional electron gas revealing strong Rashba spin-orbit interaction. In the side-gate quantum wire QPC, the conductance quantization in unit of 0.5(2e(2)/h) was mostly observed in the various samples with different dimensions. This is in contrast to the result in the split-gate QPC, where we confirmed usual (2e(2)/h) conductance quantization. Since those results were observed under zero magnetic field, the 0.5(2e(2)/h) quantization could be attributed not to the spin splitting but to the possible spin polarized transport due to the mode coupling between the one-dimensional subbands expected in sufficiently narrow adiabatic constrictions. (C) 2003 Published by Elsevier B.V.

    DOI

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    3
    被引用数
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  • Observation of e(2)/h conductance steps in a side-gate point contact on In0.75Ga0.25As/In0.75Al0.25As heterostructure

    T Kita, S Gozu, Y Sato, S Yamada

    JOURNAL OF SUPERCONDUCTIVITY   16 ( 2 ) 327 - 329  2003年04月  [査読有り]

     概要を見る

    In 1996, it was suggested by K.J. Thomas et al. (Phys. Rev. Lett. 77, 135 (1996)) that 0.7(2e(2)/h) conductance structure in Quasi-1DEG (Q1DEG) at GaAs/AlGaAs heterostructure might be related to spin polarization at zero magnetic field. We have recently studied spontaneous spin-splitting in the 2DEGs formed at normal metamorphic In0.75Ga0.25As/In0.75Al0.25As heterojunctions grown on GaAs substrates and obtained the value of less than or similar to10 meV as the zero-field splitting at Fermi level (Y. Sato et al., J. Appl. Phys. 89, 8017 (2001)). In this work, we attempted to observe spin-related phenomena in this heterojunction Q1DEGs at zero magnetic field. We observed e(2)/h conductance steps in low electron concentration side-gate point contact.

  • Conductance fluctuations in quantum wires formed at spin-splitting narrow gap heterojunctions

    S Yamada, Y Sato, T Kita, S Gozu

    COMPOUND SEMICONDUCTORS 2001   ( 170 ) 345 - 349  2002年  [査読有り]

     概要を見る

    Conductance fluctuations in quasi-ballistic quantum wires formed at spontaneously spin-splitted heterojunctions have been measured and discussed. The fluctuation amplitude was found to likely decrease when an applied magnetic field increased and when a gate voltage decreased. Both the applications of magnetic field and negative gate voltage are known to decrease the spin-orbit coupling constant in our heterojunction and they are expected to increase the fluctuation amplitude in anti-localization regime. The fluctuation results could, however, be explained, if we pay attentions to the fact that despite the large zero field spin-splitting,, the quantum wires am classified into those with tranport regimes of 'localization" and "weak' spin-orbit scattering due to the high mobilities.

  • Ballistic spin transport in four-terminal NiFe/In(0.7)5Ga(0.25)As structure

    Y Sato, S Gozu, T Kita, S Yamada

    JAPANESE JOURNAL OF APPLIED PHYSICS PART 2-LETTERS   40 ( 10B ) L1093 - L1096  2001年10月  [査読有り]

     概要を見る

    Spin-injection experiments in NiFe/two-dimensional electron gas (2DEG)/NiFe four-terminal devices are described. The 2DEG was confined at a modulation-doped In0.75Ga0.25As/In0.75Al0.25As heterojunction interface. NiFe source-drain electrodes were located similar to1 mum apart and two voltage probes were fabricated between them. The separation between the NiFe electrodes was thus almost less than both the mean free path (similar to2 mum) and the spin-diffusion length (&gt; 1 mum) of the 2DEG. In nonlocal four-terminal measurements, where a constant current (i) was sent through one NiFe to one ohmic electrode, the two-terminal magnetoresistance (R-2t = exhibited a spin-valve-like effect, while R-4t = V-4t/i showed a resistance hysteresis. The amplitude of the latter amounted to almost 12% of the R-4t (B = 0) at 1.5 K, the extent of which was one order of magnitude larger than those so far reported. These results suggest the importance of a quasi-ballistic as well as a spin-coherent coupling between the two NiFe electrodes, which may crucial in the future operation of spin field-effect transistors (FETs).

    DOI

  • Critical layer thickness study in In0.75Ga0.25As/In0.5Al0.5As pseudomorphic resonant tunneling diode structure grown on GaAs substrates

    S Gozu, T Kita, T Kikutani, S Yamada

    JOURNAL OF CRYSTAL GROWTH   227   161 - 166  2001年07月  [査読有り]

     概要を見る

    We have studied critical layer thickness (CLT) in an In0.75Ga0.25As resonant tunneling diode structure grown on a GaAs substrate, ia an InAlAs step-graded buffer (SGB) with two types of inverse step(IS)-SGB. We have observed red or blue shift in photoluminescence spectra and CLT change depending on SGB condition. This change reflects from the difference of residual strain InAlAs SGBs adopted here.,(C) 2001 Elsevier Science B.V. All rights reserved.

    DOI

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    3
    被引用数
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  • Characterization of high indium content metamorphic InGaAs/InAlAs modulation-doped heterostructures

    S Gozu, T Kita, Y Sato, S Yamada, M Tomizawa

    JOURNAL OF CRYSTAL GROWTH   227   155 - 160  2001年07月  [査読有り]

     概要を見る

    We have studied electronic and structural characterizations of high indium content metamorphic InGaAs/InAlAs modulation-doped heterostructures. An improved low-temperature electron mobility of mu (e) = 5.45 x 10(5) cm(2) Vs in [(1) over bar 1 0] was confirmed for a directed Hall-bar sample when Si-doped InAlAs layer was slightly etched. In addition, inplane mobility anisotropy of 40% between [(1) over bar 1 0] and [1 1 0] directions. We confirmed. This anisotropy seems to br originated fi om the different undulation period between[(1) over bar 1 0] and [1 1 0] directions. We theoretically calculated electron mobility taking both alloy disorder scattering and background impurity scattering into account. It is found that the calculated and experimental values are in good agreement. (C) 2001 Elsevier Science B.V. All rights reserved.

    DOI

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    18
    被引用数
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  • Large spontaneous spin splitting in gate-controlled two-dimensional electron gases at normal In0.75Ga0.25As/In0.75Al0.25As heterojunctions

    Y Sato, T Kita, S Gozu, S Yamada

    JOURNAL OF APPLIED PHYSICS   89 ( 12 ) 8017 - 8021  2001年06月  [査読有り]

     概要を見る

    Amounts of spontaneous spin splittings were estimated from low-temperature magnetoresistances in two-dimensional electron gases created at In0.75Ga0.25As/In0.75Al0.25As heterojunctions under a gate bias. Typical sheet electron densities and mobilities in the raw wafers were similar to1.0 x 10(12)/cm(2) and 2-5 x 10(5) cm(2)/V s at 1.5 K, respectively. A maximum spin-orbit coupling constant alpha (zero) of similar to 30(x10(-12) eV m) was obtained for the van der Pauw sample. In gated Hall-bar samples, a decrease in the alpha (zero) value with decreasing gate voltage (V-g) was first confirmed in a normal heterojunction. The main origin for such a large alpha (zero), which is a few times larger than any previously reported, was found to be a structure-dependent so-called interface contribution in the Rashba term. (C) 2001 American Institute of Physics.

    DOI

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    202
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  • Large spontaneous spin-splitting and enhanced effective g-factor in two-dimensional electron gases at In0.75Ga0.25As/In0.75Al0.25As metamorphic heterojunctions

    T Kita, Y Sato, S Gozu, S Yamada

    PHYSICA B   298 ( 1-4 ) 65 - 69  2001年04月  [査読有り]

     概要を見る

    We have estimated spin-splitting energy of two-dimensional electron gases formed at metamorphic In0.75Ga0.25As/In0.75Al0.25As heterojunctions by analyzing magneto-resistance traces up to 10 T. This heterojunction often reveals a large spontaneous spin-splitting at low fields, while at high fields, Zeeman splitting becomes dominant. We have investigated and compared the two sanples; one reveals beating oscillation and hence has a spontaneous or zero-field spin-splitting and another does not. In the former sample, if we assume the equal sign for both the spin-splittings, the dependency of the absolute splitting energy on the magnetic field is found to have a minimum (Delta = 2 meV) at about 3.5 T, in which we also confirmed a zero-field spin-splitting of Delta (0) = 11.04meV and very much enhanced g* = - 42.0 at 1.5 T. In contrast, effective g-factor (g*) obtained at high fields in the latter sample is g* = - 7.7 at 1.5 T, which is fairly smaller than that in the former. Origins of those features are discussed and the possibility of linear spin-splitting dependency on magnetic field is pointed out. (C) 2001 Published by Elsevier Science B.V.

    DOI

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    19
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  • Residual strain dependence of zero field spin-splitting in high indium content metamorphic InGaAs/InAlAs modulation doped heterostructures

    S Gozu, T Kita, H Sato, Y Sato, K Fujii, T Ohyama, S Yamada

    PROCEEDINGS OF THE 10TH INTERNATIONAL CONFERENCE ON NARROW GAP SEMICONDUCTORS AND RELATED SMALL ENERGY PHENOMENA, PHYSICS AND APPLICATIONS   2   42 - 44  2001年  [査読有り]

     概要を見る

    In this work, we are studying the effects of interface strain on the amount of spin-orbit coupling constant of the two-dimensional electron gas formed at the heterointerface, high In-content InGaAs/InAlAs. Tuning of the interface strain is carried out by changing the step-graded buffer (SGB) layer with additional inverse steps (ISs). Estimations of photoluminescence, far-infrared absorption and magnetoresistance measurement suggest that, although a slight extent of residual strain still remains in a case of normal SGB, the residual strain is found to decrease, if an appropriate IS layer is adopted, Associating with this, the decreases of the band gap and electron effective mass were observed together with the increase of the spin-orbit coupling constant.

  • Electrical spin-injection into a two-dimensional electron gas

    Y Sato, S Gozu, T Kita, S Yamada

    PROCEEDINGS OF THE 10TH INTERNATIONAL CONFERENCE ON NARROW GAP SEMICONDUCTORS AND RELATED SMALL ENERGY PHENOMENA, PHYSICS AND APPLICATIONS   2   248 - 250  2001年  [査読有り]

     概要を見る

    We study the electrical spin-injection and detection of spin-polarized electrons in ferromagnetic electrode - two-dimensional electron gas (2DEG) system. The 2DEG was formed at In0.75Ga0.25As/In0.75Al0.25As heterointerface and NiFe electrodes were deposited on the side surface of the mesa containing channel layer. The NiFe electrodes (width=F1:0.5, and F2:3mum) were located 1 mum apart, which was less than the mean free-path (similar to2mum) of the 2DEG, and two voltage probes were fabricated between them. We confirmed by SdH oscillations that electrons indeed transport from F1 to F2 through the 2DEG. In non-local geometry below 1.5K, we observed a spin-valve like effect of similar to0.2% in source-drain resistance of despite including the single ferromagnet/2DEG interface in the current pass. We also observed the hysterisis behavior of similar to12% in four-terminal resistance below 1.5K, Both signals were found to disappear at 200K. This temperature dependency strongly suggests that these signals could not be explained only by the local Hall effect, since the sheet electron density, N-S, in our heterostructure is almost kept constant from 0.3 to 200K.

▼全件表示

Misc

  • Tunable Dual-Wavelength Heterogeneous Quantum Dot Laser Diode with a Silicon External Cavity

    Tomohiro Kita, Atsushi Matsumoto, Naokatsu Yamamoto, Hirohito Yamada

    Journal of Lightwave Technology   36 ( 2 ) 219 - 224  2018年01月

     概要を見る

    We propose a tunable dual-wavelength heterogeneous quantum dot laser diode. The tunable dual-wavelength laser consists of a quantum dot semiconductor optical amplifier as the optical gain medium and an external cavity fabricated from silicon photonics technology as the wavelength tunable filter. We successfully demonstrated dual-wavelength lasing oscillation by tuning the difference frequency from approximately 34 to 400 GHz.

    DOI

  • Demonstration of 1-μm-band Si-photonics-based quantum dot heterogeneous tunable laser

    A. Matsumoto, K. Akahane, T. Umezawa, N. Yamamoto, H. Yamada, T. Kita

    2018 Conference on Lasers and Electro-Optics, CLEO 2018 - Proceedings   2018  2018年

     概要を見る

    © 2018 OSA. We present a Si-photonics-based quantum dot heterogeneous tunable lasers in the 1-μm band. Optical devices using Si-photonics-based PIC in the 1-μm band probably have not been reported yet.

    DOI

  • Silicon photonic wavelength tunable laser diode with low loss direct heating phase shifter

    Tomohiro Kita, Yuto Chiba, Hirohito Yamada

    14th International Conference on Group IV Photonics, GFP 2017     125 - 126  2017年10月

     概要を見る

    We proposed and demonstrated a compact and low propagation loss thermo-optical phase shifter using a multi-mode interference. The calculated insertion loss of designed MMI phase shifter was approximately 0.05 dB. The fabricated phase shifter shows high speed and low power consumption. The wavelength tunable laser diode with two ring resonators loaded the MMI phase shifters was fabricated. The wavelength tuning operation with low power consumption was successfully demonstrated.

    DOI

  • Heterogeneous lasers with silicon photonic external cavity

    Tomohiro Kita, Shotaro Takei, Atsushi Matsumoto, Naokatsu Yamamoto, Hirohito Yamada

    Optics InfoBase Conference Papers   Part F78-JSAP 2017  2017年01月

  • Differential frequency tunable Dual-Mode heterogeneous QD laser with Si PIC

    A. Matsumoto, T. Umezawa, K. Akahane, N. Yamamoto, H. Yamada, T. Kita

    Optics InfoBase Conference Papers   2017  2017年

     概要を見る

    We proposed a tunable dual-mode heterogeneous quantum dot laser diode with a Siphotonics-based photonic integrated circuit, and successfully demonstrated dual-mode lasing oscillation by tuning the differential frequency from approximately 20 GHz to 200 GHz.

    DOI

  • Silicon Photonic Wavelength-Tunable Lasers for High-Capacity Optical Communication Systems

    Tomohiro Kita, Hiroyuki Yamazaki, Naokatsu Yamamoto, Hirohito Yamada

    2017 OPTICAL FIBER COMMUNICATIONS CONFERENCE AND EXHIBITION (OFC)   Part F40-OFC 2017  2017年

     概要を見る

    Silicon photonic wavelength-tunable laser diodes consist of a wavelength-tunable filter with double silicon ring resonators and a compound semiconductor optical amplifier. Narrow spectral linewidth lasers for digital coherent optical communication systems and quantum dot heterogeneous laser diodes were demonstrated. The combination of silicon photonics and compound semiconductor technology leads to a breakthrough in the development of effective and compact integrated light sources for a wide range of application fields.

    DOI

  • Quantum-dot-based advanced photonic devices and its applications

    A. Matsumoto, K. Akahane, T. Umezawa, T. Kita, K. Utaka, N. Yamamoto

    Optics InfoBase Conference Papers   2017  2017年

     概要を見る

    Quantum dot (QD) is one of the attractive materials. In this paper, we focus on advanced photonic devices using QD structure and its applications for the next generation access networks.

    DOI

  • Silicon Photonic Wavelength-Tunable Lasers for High-Capacity Optical Communication Systems

    Tomohiro Kita, Hiroyuki Yamazaki, Naokatsu Yamamoto, Hirohito Yamada

    2017 OPTICAL FIBER COMMUNICATIONS CONFERENCE AND EXHIBITION (OFC)   Part F40-OFC 2017  2017年

     概要を見る

    Silicon photonic wavelength-tunable laser diodes consist of a wavelength-tunable filter with double silicon ring resonators and a compound semiconductor optical amplifier. Narrow spectral linewidth lasers for digital coherent optical communication systems and quantum dot heterogeneous laser diodes were demonstrated. The combination of silicon photonics and compound semiconductor technology leads to a breakthrough in the development of effective and compact integrated light sources for a wide range of application fields.

    DOI

  • Quantum-dot-based advanced photonic devices and its applications

    A. Matsumoto, K. Akahane, T. Umezawa, T. Kita, K. Utaka, N. Yamamoto

    Optics InfoBase Conference Papers   2017  2017年

     概要を見る

    Quantum dot (QD) is one of the attractive materials. In this paper, we focus on advanced photonic devices using QD structure and its applications for the next generation access networks.

    DOI

  • Differential frequency tunable Dual-Mode heterogeneous QD laser with Si PIC

    A. Matsumoto, T. Umezawa, K. Akahane, N. Yamamoto, H. Yamada, T. Kita

    Optics InfoBase Conference Papers   2017   1 - 2  2017年

     概要を見る

    We proposed a tunable dual-mode heterogeneous quantum dot laser diode with a Siphotonics-based photonic integrated circuit, and successfully demonstrated dual-mode lasing oscillation by tuning the differential frequency from approximately 20 GHz to 200 GHz.

    DOI

  • シリコン細線光導波路におけるラマン散乱を利用した光キャリアコンバータの検討 (光エレクトロニクス)

    北 智洋, 山田 博仁

    電子情報通信学会技術研究報告 = IEICE technical report : 信学技報   116 ( 349 ) 29 - 32  2016年12月

    CiNii

  • Instability of silicon photonic wavelength tunable laser diodes due to the nonlinear optical effect of silicon

    Tomohiro Kita, Hirohito Yamada

    Conference Digest - IEEE International Semiconductor Laser Conference    2016年12月

     概要を見る

    © 2016 IEICE-ES. The silicon photonic wavelength tunable laser diode is a good candidate for the integrated light source of the digital coherent optical communication system.However, optical nonlinear effects easily occur due to the strong light confinement of Si photonic wire waveguides. The impact on laser operation caused by nonlinearity was discussed.

  • Narrow Spectral Linewidth Silicon Photonic Wavelength Tunable Laser Diode for Digital Coherent Communication System

    Tomohiro Kita, Rui Tang, Hirohito Yamada

    IEEE JOURNAL OF SELECTED TOPICS IN QUANTUM ELECTRONICS   22 ( 6 )  2016年11月

     概要を見る

    We demonstrated wavelength tunable laser diodes with Si-wire waveguide ring resonators as an external optical cavity. The footprint of the optical cavity including the semiconductor optical amplifier is as small as 0.8 mm x 0.6 mm which is less 1/10 of those made of silicon oxinitride material. Wavelength tuning range of approximately 55 nm was demonstrated, which covers entire L-band of the optical communication wavelength system. Furthermore, a spectral linewidth narrower than 100 kHz was obtained by optimizing the design of the external optical cavity. The optical nonlinearity of silicon is described and the influence on laser oscillation is also discussed.

    DOI

  • Heterogeneous quantum dot/silicon photonics-based wavelength-tunable laser diode with a 44 nm wavelength-tuning range

    Tomohiro Kita, Naokatsu Yamamoto, Atsushi Matsumoto, Tetsuya Kawanishi, Hirohito Yamada

    JAPANESE JOURNAL OF APPLIED PHYSICS   55 ( 4 )  2016年04月

     概要を見る

    A heterogeneous wavelength-tunable laser diode combining quantum dot and silicon photonics technologies is proposed. A compact wavelength-tunable filter with two ring resonators was carefully designed and fabricated using silicon photonics technology. The tunable laser combining the wavelength-tunable filter and an optical amplifier, which includes InAs quantum dots, achieved a 44.0 nm wavelength-tuning range at around 1250 nm. The broadband optical gain of the quantum dot optical amplifier was effectively used by the optimized wavelength-tunable filter. This heterogeneous wavelength-tunable laser diode could become a breakthrough technology for high-capacity data transmission systems. (C) 2016 The Japan Society of Applied Physics

    DOI

  • Advanced photonic ICT devices and their system applications using quantum-dot technology

    Naokatsu Yamamoto, Kouichi Akahane, Toshimasa Umezawa, Atsushi Matsumoto, Atsushi Kanno, Tetsuya Kawanishi, Tetsuya Kawanishi, Tomohiro Kita, Hirohito Yamada

    Asia Communications and Photonics Conference, ACPC 2015    2015年12月

     概要を見る

    Quantum-dot nanotechnology is attractive for use in advanced photonic devices that will augment the available optical-frequency resources and will increase the number of wavelength channels usable by wired and wireless networks in short/middle-range communication systems. © 2015 OSA.

    DOI

  • Ultra-compact wavelength-tunable quantum-dot laser with silicon-photonics double ring filter

    Tomohiro Kita, Naokatsu Yamamoto, Tetsuya Kawanishi, Hirohito Yamada

    APPLIED PHYSICS EXPRESS   8 ( 6 )  2015年06月

     概要を見る

    Compact, wavelength-tunable light sources are desired for the enhancement of information communication technology and bio-imaging applications. We propose a compact, wavelength-tunable laser diode with a wide wavelength-tunable range around 1230 nm consisting of a quantum-dot optical amplifier and a silicon photonic tunable filter. High-quality InAs quantum dots grown with the sandwiched sub-nano separator technique were used as the optical gain medium. The wavelength-tunable filter was constructed with ring resonators fabricated using silicon photonics. The single-mode laser oscillation was demonstrated with a 28.5-nm wavelength-tunable range. (C) 2015 The Japan Society of Applied Physics

    DOI

  • シリコンフォトニクスを用いたコヒーレント光通信用狭線幅波長可変レーザの開発

    北 智浩

    光技術コンタクト2015年4月号   53 ( 4 ) 13 - 19  2015年04月

    記事・総説・解説・論説等(商業誌、新聞、ウェブメディア)  

    CiNii

  • Narrow-spectral-linewidth silicon photonic wavelength-tunable laser with highly asymmetric Mach-Zehnder interferometer

    Rui Tang, Tomohiro Kita, Hirohito Yamada

    OPTICS LETTERS   40 ( 7 ) 1504 - 1507  2015年04月

     概要を見る

    We propose a narrow-spectral-linewidth silicon photonic wavelength-tunable laser with a novel external wavelength-tunable filter, which consists of two silicon ring resonators with different circumferences and a highly asymmetric Mach-Zehnder interferometer (MZI), the two optical paths of which have significantly different lengths. Calculations and experimental results indicated that the gain difference between longitudinal modes was increased by the highly asymmetric MZI. Consequently, a narrow spectral linewidth of 12 kHz and a stable single-mode oscillation were obtained. (C) 2015 Optical Society of America

    DOI

  • Optimum waveguide-core size for reducing device property distribution of Si-wire waveguide devices

    Munetoshi Soma, Tomohiro Kita, Yuichiro Tanushi, Munehiro Toyama, Miyoshi Seki, Nobuyuki Yokoyama, Minoru Ohtsuka, Hirohito Yamada

    JAPANESE JOURNAL OF APPLIED PHYSICS   54 ( 4 )  2015年04月

     概要を見る

    We investigated the waveguide-core size distribution of ring resonators fabricated on a 300mm silicon-on-insulator (SOI) wafer using a CMOS-compatible process featuring ArF immersion lithography. These ring resonators were constructed in a Si-wire waveguide with a standard core size of 400nm width and 220nm height. The group refractive indices of the waveguide were derived from the transmission spectra of the ring resonators. From the deviation of these group refractive indices, the waveguide-core width distribution was estimated to be 5 nm, and the waveguide-core height distribution was estimated to be 1 nm. Moreover, the device property distribution of various Si-wire waveguide depended on the estimated fabrication error was calculated. The waveguide core with the smallest device property distribution had a 540nm width and a 160nm height, and this waveguide has a device property distribution of 2/3 value compared with the standard core size. (C) 2015 The Japan Society of Applied Physics

    DOI

  • C-3-25 高非対称マッハ・ツェンダー干渉計を装荷した狭線幅シリコンフォトニック波長可変レーザ(シリコンフォトニクス(2),C-3.光エレクトロニクス,一般セッション)

    唐 睿, 北 智洋, 山田 博仁

    電子情報通信学会総合大会講演論文集   2015 ( 1 ) 149 - 149  2015年02月

    CiNii

  • Ultra-compact Wavelength Tunable Quantum Dot Laser with Silicon Photonic External Cavity

    Tomohiro Kita, Naokatsu Yamamoto, Tetsuya Kawanishi, Hirohito Yamada

    2015 CONFERENCE ON LASERS AND ELECTRO-OPTICS (CLEO)     2267  2015年

     概要を見る

    Ultra-compact wavelength tunable laser diode with wide tunability was successfully developed with combining quantum dot optical amplifier and silicon micro-ring filters. The single mode laser oscillation was demonstrated with 25 nm wavelength tuning range.

    DOI

  • Ultra-compact Wavelength Tunable Quantum Dot Laser with Silicon Photonic External Cavity

    Tomohiro Kita, Naokatsu Yamamoto, Tetsuya Kawanishi, Hirohito Yamada

    2015 CONFERENCE ON LASERS AND ELECTRO-OPTICS (CLEO)   2015-August   2267  2015年

     概要を見る

    Ultra-compact wavelength tunable laser diode with wide tunability was successfully developed with combining quantum dot optical amplifier and silicon micro-ring filters. The single mode laser oscillation was demonstrated with 25 nm wavelength tuning range.

    DOI

  • Demonstration of Silicon Photonic Hybrid Ring-Filter External Cavity Wavelength Tunable Lasers

    K. Sato, N. Kobayashi, M. Namiwaka, K. Yamamoto, S. Watanabe, T. Kita, H. Yamada, H. Yamazaki

    ECOC 2015 41ST EUROPEAN CONFERENCE ON OPTICAL COMMUNICATION   2015-November  2015年

     概要を見る

    Silicon-photonic hybrid ring-filter external cavity (SHREC) tunable lasers fabricated by passive alignment techniques are demonstrated. High power, narrow linewidth and highly reliable characteristics are achieved thanks to drastically reduced losses in the laser cavity toward commercialization.

    DOI

  • 高非対称マッハ・ツェンダー干渉計装荷型シリコフォトニック波長可変レーザ (光エレクトロニクス)

    唐 睿, 北 智洋, 山田 博仁

    電子情報通信学会技術研究報告 = IEICE technical report : 信学技報   114 ( 377 ) 7 - 10  2014年12月

     概要を見る

    シリコン細線光導波路によって作製したリング共振器波長可変フィルタを外部共振器として用いた波長可変レーザは,良好な波長可変特性と100kHz以下の狭線幅動作を実証しデジタルコヒーレント光通信用光源として有望なことが示されている.より高次の変調方式に対応するためには更なる狭線幅化が必要であるが,従来型のフィルタ構造では発振線幅と縦モード間のモード利得差にはトレードオフの関係があるため,更なる狭線幅発振と安定したシングルモード発振を両立させることは難しい.本稿では非常に長い遅延線を持つ高非対称マッハ・ツェンダー干渉計を装荷することで,長い共振器長を持ちながら高いモード利得差を併せ持つフィルタ構造を設計,試作した.レーザ発振特性の測定結果から49dBの高いサイドモード抑圧比と12kHz程度の狭線幅発振が確認された.

    CiNii

  • 高非対称マッハ・ツェンダー干渉計装荷型シリコフォトニック波長可変レーザ (レーザ・量子エレクトロニクス)

    唐 睿, 北 智洋, 山田 博仁

    電子情報通信学会技術研究報告 = IEICE technical report : 信学技報   114 ( 378 ) 7 - 10  2014年12月

     概要を見る

    シリコン細線光導波路によって作製したリング共振器波長可変フィルタを外部共振器として用いた波長可変レーザは,良好な波長可変特性と100kHz以下の狭線幅動作を実証しデジタルコヒーレント光通信用光源として有望なことが示されている.より高次の変調方式に対応するためには更なる狭線幅化が必要であるが,従来型のフィルタ構造では発振線幅と縦モード間のモード利得差にはトレードオフの関係があるため,更なる狭線幅発振と安定したシングルモード発振を両立させることは難しい.本稿では非常に長い遅延線を持つ高非対称マッハ・ツェンダー干渉計を装荷することで,長い共振器長を持ちながら高いモード利得差を併せ持つフィルタ構造を設計,試作した.レーザ発振特性の測定結果から49dBの高いサイドモード抑圧比と12kHz程度の狭線幅発振が確認された.

    CiNii

  • Wide-band wavelength tunable laser diode with si photonic filter

    Tomohiro Kita, Rui Tang, Hirohito Yamada

    Conference Digest - IEEE International Semiconductor Laser Conference     149 - 150  2014年12月

     概要を見る

    We investigated the wide-band wavelength tuning operation to increase the possibility of silicon photonic wavelength tunable laser diodes which is composed semiconductor optical amplifier and silicon photonic waveguide filter. The wide-band wavelength tuning operation of 94.1 nm was demonstrated.

    DOI

  • Narrow spectral linewidth Si photonic wavelength tunable laser diode for digital coherent optical communication

    Rui Tang, Tomohiro Kita, Hirohito Yamada

    Conference Digest - IEEE International Semiconductor Laser Conference     96 - 97  2014年12月

     概要を見る

    A compact wavelength tunable laser diode for digital coherent optical communication was demonstrated with a wavelength tunable filter consisting of silicon photonic wire waveguides. Stable single-mode operation with 17.8 dBm maximum output power as well as less than 100 kHz spectral line width were obtained.

    DOI

  • C-3-24 狭線幅・高出力シリコンフォトニック波長可変レーザ(C3.光エレクトロニクス,一般セッション)

    北 智洋, 唐 睿, 山田 博仁

    電子情報通信学会ソサイエティ大会講演論文集   2014 ( 1 ) 121 - 121  2014年09月

    CiNii

  • 狭線幅シリコンフォトニック波長可変レーザモジュール (電子部品・材料)

    北 智洋, 唐 睿, 山田 博仁

    電子情報通信学会技術研究報告 = IEICE technical report : 信学技報   114 ( 185 ) 83 - 86  2014年08月

     概要を見る

    シリコン細線光導波路を用いたリング共振器波長フィルタを持つ狭線幅波長可変レーザを作製した。フットプリントは2.6mm×0.5mmと従来のSiON導波路を用いた波長可変レーザと比べて1/9の小型になり、波長可変フィルタの構造を最適化することで最大光出力40mW以上の安定したシングルモード発振、CバンドまたはLバンド全域をカバーする波長可変幅と100kHz以下の狭線幅動作を実現した。さらにフリップチップボンディングにより波長可変フィルタにSOAを集積化させた1チップシリコンフォトニック波長可変レーザを試作した。

    CiNii

  • 高非線形TiO₂光導波路による広波長帯域光発生 (光エレクトロニクス)

    北 智洋, 内島 晃司, 藪野 正裕, 逢坂 崇, 片山 竜二, 枝松 圭一, 山田 博仁

    電子情報通信学会技術研究報告 = IEICE technical report : 信学技報   114 ( 97 ) 11 - 14  2014年06月

     概要を見る

    高い非線形光学定数と大きなバンドギャップを持つTiO_2をコアとしたチャネル型導波路を用いた高波長帯域光発生デバイスに関して検討を行った。試作したTiO_2導波路において自己位相変調効果によるスペクトル広がりを確認した。数値解析によって本構造を用いたソリトン分裂による超広波長帯帯域発生の可能性について検証した。

    CiNii

  • Long external cavity Si photonic wavelength tunable laser diode

    Tomohiro Kita, Keita Nemoto, Hirohito Yamada

    JAPANESE JOURNAL OF APPLIED PHYSICS   53 ( 4 )  2014年04月

     概要を見る

    We fabricated wavelength-tunable laser diodes with external cavity consist of Si photonic wire waveguide ring resonators. About 51.5 nm wavelength tuning operation, which covers the entire L-band of the optical communication wavelength range, was obtained. The cavity length dependence of the spectral line width was verified to obtain narrower spectral linewidth. The observed spectral linewidth of 3.78 mm long cavity and 8.19 mm long cavity are 131.0 and 64.8 kHz, respectively. The advantage of long external cavity to design the narrow spectral linewidth Si photonic wavelength tunable laser diode was confirmed. (C) 2014 The Japan Society of Applied Physics

    DOI

  • CI-2-3 シリコンフォトニクスと光カプラ(CI-2.マイクロ・ナノフォトニクス集積および実装技術とその展開,ソサイエティ企画)

    山田 博仁, 奈良 匡樹, 北 智洋

    電子情報通信学会総合大会講演論文集   2014 ( 1 ) "SS - 13"-"SS-14"  2014年03月

    CiNii

  • C-3-79 位相制御機構を有するSi細線リング共振器型波長可変レーザ(シリコンフォトニクス(2),C-3.光エレクトロニクス,一般セッション)

    唐 睿, 北 智洋, 根本 景太, 澤田 延幸, 山田 博仁

    電子情報通信学会総合大会講演論文集   2014 ( 1 ) 234 - 234  2014年03月

    CiNii

  • C-4-18 シリコンフォトニック波長可変レーザ(C-4.レーザ・量子エレクトロニクス,一般セッション)

    北 智洋, 唐 睿, 根本 景太, 山田 博仁

    電子情報通信学会総合大会講演論文集   2014 ( 1 ) 254 - 254  2014年03月

    CiNii

  • High Output Power and Narrow Linewidth Silicon Photonic Hybrid Ring-Filter External Cavity Wavelength Tunable Lasers

    K. Sato, N. Kobayashi, M. Namiwaka, K. Yamamoto, T. Kita, H. Yamada, H. Yamazaki

    2014 EUROPEAN CONFERENCE ON OPTICAL COMMUNICATION (ECOC)    2014年

     概要を見る

    Si-photonic Hybrid Ring-filter External Cavity (SHREC) wavelength tunable lasers by passive alignment techniques with over 100-mW fiber-coupled power and linewidth narrower than 15 kHz along the whole C-band are demonstrated. Obtained results show excellent features of Si-photonics towards commercial products.

    DOI

  • Athermal Silicon photonic devices using hybrid polymer cladding

    Tomohiro Kita, Freddy Susanto Tan, Okihiro Sugihara, Hirohito Yamada, Toshikuni Kaino

    POF 2014 - 23rd International Conference on Plastic Optical Fibers, Proceedings     272 - 275  2014年01月

     概要を見る

    © 2014 ICPOF. The compensation of sensitivity for ambient temperature is big issue to realize Silicon photonic integrated circuits. The large positive thermo-optic coefficient of Silicon core was cancelled by the negative thermooptic coefficient of hybrid polymer cladding including rutile TiO2nanoparticles. The athermal waveguide structure with Silicon core and Hybrid polymer cladding was designed by numerical calculation.

  • Si Photonic Wavelength Tunable Laser Diode with the Phase Shifter of Longitudinal Mode

    Tomohiro Kita, Rui Tang, Keita Nemoto, Hirohito Yamada

    2014 IEEE 11TH INTERNATIONAL CONFERENCE ON GROUP IV PHOTONICS (GFP)     209 - 210  2014年

     概要を見る

    We fabricated wavelength tunable laser diodes with Si photonic wire waveguide ring resonators as an external optical cavity. The continuous wavelength tuning operation was demonstrated using by the micro heaters. Our wavelength tunable laser diode is suitable for digital coherent optical transmission systems based on wavelength division multiplexing.

    DOI

  • Recent progress of optical interconnect devices using photonic polymers

    O. Sugihara, T. Kita, D. Inoue, F. S. Tan, A. Hattori, A. Kawasaki, M. Sato, T. Yamashita, M. Mizuno, S. Okada, M. Kagami, M. Tsuchimori, O. Watanabe, H. Yamada, T. Kaino

    POF 2014 - 23rd International Conference on Plastic Optical Fibers, Proceedings     87  2014年01月

     概要を見る

    © 2014 ICPOF. We present recent progress of photonic polymers and waveguide-type device fabrication for high performance optical integrated circuit modules.

  • Si photonic wavelength tunable laser diode for digital coherent optical communication

    T. Kita, K. Nemoto, K. Watanabe, H. Yamazaki, H. Yamada

    2013 18th OptoElectronics and Communications Conference Held Jointly with 2013 International Conference on Photonics in Switching, OECC/PS 2013    2013年10月

     概要を見る

    We fabricated wavelength tunable laser diodes with Si photonic wire waveguide ring resonators as an external optical cavity. Less than 100 kHz narrow spectral linewidth was obtained with small footprint. Our wavelength tunable laser diodes with narrow spectral linewidth are promising light source for practical use in digital coherent optical transmission systems. © 2013 IEICE.

  • シリコンフォトニクス波長可変レーザーの高出力・安定動作 (レーザ・量子エレクトロニクス)

    北 智洋, 根本 景太, 山田 博仁

    電子情報通信学会技術研究報告 = IEICE technical report : 信学技報   113 ( 264 ) 85 - 88  2013年10月

     概要を見る

    シリコン細線光導波路を用いたリング共振器波長フィルターを持つ狭線幅波長可変レーザーを作製した.フットプリントは,2.6mm×0.5mmと従来のSiON導波路を用いた波長可変レーザーと比べて1/9の小型になり,波長可変フィルターの構造を最適化することで最大光出力34.9mWの安定したシングルモード発振,Lバンド全域をカバーする67.6nmの波長可変幅と100kHz以下の狭線幅動作を実現した.

    CiNii

  • シリコンフォトニクス波長可変レーザーの高出力・安定動作 (光エレクトロニクス)

    北 智洋, 根本 景太, 山田 博仁

    電子情報通信学会技術研究報告 = IEICE technical report : 信学技報   113 ( 263 ) 85 - 88  2013年10月

     概要を見る

    シリコン細線光導波路を用いたリング共振器波長フィルターを持つ狭線幅波長可変レーザーを作製した.フットプリントは,2.6mm×0.5mmと従来のSiON導波路を用いた波長可変レーザーと比べて1/9の小型になり,波長可変フィルターの構造を最適化することで最大光出力34.9mWの安定したシングルモード発振,Lバンド全域をカバーする67.6nmの波長可変幅と100 kHz以下の狭線幅動作を実現した.

    CiNii

  • C-3-50 Si細線光導波路リング∠MZIフィルタを用いた狭線幅波長可変レーザ(光集積デバイス,C-3.光エレクトロニクス,一般セッション)

    根本 景太, 北 智洋, 山田 博仁

    電子情報通信学会ソサイエティ大会講演論文集   2013 ( 1 ) 172 - 172  2013年09月

    CiNii

  • 300mm基板上にArF液侵リソグラフィーを用いて作製したシリコンフォトニクスデバイス (レーザ・量子エレクトロニクス)

    北 智洋, 田主 裕一朗, 奈良 匡樹, 平野 秀, 外山 宗博, 関 三好, 越野 圭二, 横山 信幸, 大塚 実, 杉山 曜宣, 石塚 栄一, 佐野 作, 堀川 剛, 山田 博仁

    電子情報通信学会技術研究報告 = IEICE technical report : 信学技報   113 ( 100 ) 1 - 5  2013年06月

     概要を見る

    ArF液侵リソグラフィー技術を用いて300mm SOIウェハ上にチャネル型シリコン細線導波路,方向性結合器,リング共振器を作製し,光学特性を評価した.評価結果は数値計算結果との良い一致を示し,シリコンフォトニクスデバイス作製に本プロセス工程を用いることの有効性が確認された.

    CiNii

  • Nonlinear optical photonic crystal waveguide with TiO2 material

    Koji Uchijima, Tomohiro Kita, Hirohito Yamada

    OXIDE-BASED MATERIALS AND DEVICES IV   8626  2013年

     概要を見る

    Titanium dioxide (TiO2) has several attractive properties such as high linear and nonlinear refractive indices and the wide bandgap for applying the nonlinear optical devices. We have been studied channel waveguides with TiO2 as the submicron size core to verify their feasibility as the nonlinear optical devices. In this study, we analyzed optical propagation in the TiO2 photonic crystal waveguide and demonstrated the enhanced optical nonlinearity due to slow light effect.

    DOI

  • Anomalous localization modes in Bragg-grating based on high index-difference waveguide

    Tomohiro Kita, Koji Uchijima, Hirohito Yamada

    SILICON PHOTONICS VIII   8629  2013年

     概要を見る

    We observed photonic band-gap disappearance on Bragg-grating wavelength filters with Si photonic-wire waveguides, and studied the physical mechanism with theoretical and numerical analyses. This is a unique phenomenon observed in channel waveguides with very high index-contrast between the waveguide core and cladding materials. The photonic band-gap disappearance was observed in structures where two different optical field distributions of standing wave degenerate.

    DOI

  • Narrow spectral linewidth and high output power Si photonic wavelength tunable laser diode

    Tomohiro Kita, Keita Nemoto, Hirohito Yamada

    IEEE International Conference on Group IV Photonics GFP     152 - 153  2013年

     概要を見る

    We fabricated wavelength tunable laser diodes with Si photonic wire waveguide ring resonators as an external optical cavity. Less than 100 kHz narrow spectral linewidth was obtained with small footprint. Our wavelength tunable laser diode shows sufficient good performance for practical use in digital coherent optical transmission systems. © 2013 IEEE.

    DOI

  • Uniform characteristics of Si-wire waveguide devices fabricated on 300 mm SOI wafers by using ArF immersion lithography

    Yuichiro Tanushi, Tomohiro Kita, Munehiro Toyama, Miyoshi Seki, Keiji Koshino, Nobuyuki Yokoyama, Minoru Ohtsuka, Akinobu Sugiyama, Eiichi Ishitsuka, Tsukuru Sano, Tsuyoshi Horikawa, Hirohito Yamada

    IEEE International Conference on Group IV Photonics GFP     105 - 106  2013年

     概要を見る

    We have investigated characteristics uniformity of Si-wire waveguide devices formed on 300 mm SOI wafers by using ArF immersion lithography process. Very low dispersion of group indices within wafers was confirmed from measurements of asymmetric Mach-Zhender interferometers. © 2013 IEEE.

    DOI

  • シリコン細線光導波路を用いた狭線幅波長可変レーザーの開発

    北 智洋, 根本 景太, 山田 博仁

    電子情報通信学会技術研究報告. R, 信頼性   112 ( 180 ) 111 - 114  2012年08月

     概要を見る

    シリコン細線光導波路を用いたリング共振器波長フィルタを持つ狭線幅波長可変レーザーを作製した。半導体光増幅器と波長可変フィルタを含めたフットプリントは、2.73mm×0.89mmと従来のSiON導波路を用いた波長可変レーザーと比べて1/3の小型化を実現した。共振器構造の最適化によりLバンド全域をカバーする44nmの波長可変幅と100kHz以下の狭線幅動作を実現した。

    CiNii

  • Narrow-Spectral-Linewidth Wavelength-Tunable Laser Diode with Si Wire Waveguide Ring Resonators

    Keita Nemoto, Tomohiro Kita, Hirohito Yamada

    APPLIED PHYSICS EXPRESS   5 ( 8 )  2012年08月

     概要を見る

    We fabricated wavelength-tunable laser diodes with Si wire waveguide ring resonators as an external optical cavity. The footprint of the optical cavity including the semiconductor optical amplifier is as small as 2.73 x 0.89 mm(2), which is about 1/5 of those made of silicon oxinitride material. About 44-nm-wavelength tuning operation, which covers the entire L-band of the optical communication wavelength range, was obtained. Furthermore, spectral linewidth narrower than 100 kHz was obtained by optimizing the design of the external optical cavity. The tunable laser diodes with narrow spectral linewidth are suitable as light sources for digital coherent optical transmission systems. (C) 2012 The Japan Society of Applied Physics

    DOI

  • Analysis of Phase Matching Conditions for Generating Second Harmonic in ZnO Channel Waveguides

    Yuta Taira, Tomohiro Kita, Edgar Yoshio Morales Teraoka, Hirohito Yamada

    JAPANESE JOURNAL OF APPLIED PHYSICS   51 ( 4 )  2012年04月

     概要を見る

    We describe a phase-matching scheme for generating the second harmonic in ZnO channel waveguides using a modal phase-matching (MPM) method. We found that MPM can be achieved between the TM00 mode of the fundamental wave and the TM02 mode of the second-harmonic wave by using structural dispersion of the waveguide mode. Furthermore, we calculated the normalized conversion efficiency by taking the overlap integral of each waveguide mode and the effective area of the fundamental wave into account, and obtained a sufficiently high conversion efficiency. These results show that ZnO channel waveguides are very attractive for generating second-harmonic devices. (C) 2012 The Japan Society of Applied Physics

    DOI

  • C-3-44 Si細線光導波路リング共振器フィルタを用いた狭線幅波長可変レーザ(C-3.光エレクトロニクス,一般セッション)

    根本 景太, 北 智洋, 山田 博仁

    電子情報通信学会総合大会講演論文集   2012 ( 1 ) 193 - 193  2012年03月

    CiNii

  • シリコン細線光導波路を用い/ T 狭線幅波長可変レーザ一の開発

    北智洋

    信学技報   112 ( 183 ) 111 - 114  2012年

    CiNii

  • Narrow spectral linewidth wavelength tunable laser with Si photonic-wire waveguide ring resonators

    Keita Nemoto, Tomohiro Kita, Hirohito Yamada

    IEEE International Conference on Group IV Photonics GFP     216 - 218  2012年

     概要を見る

    We fabricated wavelength tunable laser diodes with Si-wire waveguide ring resonators as an external optical cavity. Less than 100 kHz narrow spectral linewidth was obtained by optimizing design of the ring resonators. The wavelength tunable laser diodes with narrow spectral linewidth are suitable as light sources for digital coherent optical transmission systems. © 2012 IEEE.

    DOI

  • C-3-48 Si細線光導波路リング共振器フィルタを用いた波長可変レーザの狭スペクトル線幅化の検討(C-3.光エレクトロニクス,一般セッション)

    菊池 健司, 鈴木 健, 北 智洋, 山田 博仁

    電子情報通信学会総合大会講演論文集   2011 ( 1 ) 223 - 223  2011年02月

    CiNii

  • Wavelength Tunable Laser Diodes with Si-Wire Waveguide Ring Resonator Wavelength Filters

    Ken Suzuki, Tomohiro Kita, Hirohito Yamada

    SILICON PHOTONICS VI   7943  2011年

     概要を見る

    We fabricated wavelength tunable laser diodes consisting of ring resonator wavelength filters with Si-wire waveguides. More than 45 nm wavelength tuning operation was obtained by about 100 mW heating power. We also measured spectral linewidth of the tunable laser, and observed about 200 kHz of spectral linewidth.

    DOI

  • Variation of optical properties by the crystalline phase transition of polycrystalline silicon

    Hidenori Iwata, Tomohiro Kita, Hirohito Yamada

    SILICON PHOTONICS VI   7943  2011年

     概要を見る

    We studied a characteristics trimming technique in Si photonic-wire waveguide devices. In order to trimming device properties, we utilized refractive index change of amorphous silicon when it crystallizes by annealing. We fabricated MZI devices with amorphous silicon waveguides, and demonstrated the trimming of the transmission spectra by thermal annealing and also laser annealing after finished the device fabrication process. We observed 5.2 % of the refractive index change owing to crystallization by annealing in a nitrogen atmosphere and 5.8% of change by laser crystallization.

    DOI

  • Fabrication of ZnO channel waveguides for nonlinear optical applications

    Edgar Yoshio Morales Teraoka, Tomohiro Kita, Atsushi Tsukazaki, Masashi Kawasaki, Hirohito Yamada

    OXIDE-BASED MATERIALS AND DEVICES II   7940  2011年

     概要を見る

    We present a fabrication procedure for ZnO channel waveguides intended for nonlinear optical applications. Ar ion milling was used to etch the single crystal thin film samples, and the effects of bias power, chamber pressure and Ar flow rate were investigated, finding optimal parameters for waveguide fabrication. The effect of sidewall roughness was estimated by comparing the results of cut-back measurements and an analytical model. We show an easy and effective method for the fabrication of ZnO channel waveguides.

    DOI

  • Nonlinear optical waveguides with rutile TiO(2)

    Koichi Abe, Edgar Yoshio Morales Teraoka, Tomohiro Kita, Hirohito Yamada

    OXIDE-BASED MATERIALS AND DEVICES II   7940  2011年

     概要を見る

    We investigated a possibility of making rutile TiO(2) channel waveguides for nonlinear optical applications. Single mode conditions, the group velocity dispersion and the nonlinear-optical parameters for the rutile TiO(2) channel waveguides were calculated using the finite-element method. We also fabricate channel waveguides with rutile TiO(2) using reactive ion etching. The propagation loss measured by the cut-back method was around 6 dB/mm. According to our simulation, around 70 nm of spectral broadening owing to the self-phase modulation will be expected by a pumping optical pulse with 360 W peak power.

    DOI

  • Second and Third-Order Nonlinear Optical Effects in ZnO Channel Waveguides

    Tomohiro Kita, Yoshio Morales Teraoka, Yoshitomo Okawachi, Atsushi Tsukazaki, Masashi Kawasaki, Alexander L. Gaeta, Hirohito Yamada

    2011 CONFERENCE ON LASERS AND ELECTRO-OPTICS (CLEO)    2011年

     概要を見る

    We demonstrate simultaneous self-phase modulation and second harmonic generation in ZnO channel waveguides. We estimate a value of gamma = 13.9 +/- 3.0 W(-1)m(-1), indicating that ZnO offers promise as a platform for nonlinear devices. (C)2011 Optical Society of America

  • Zero photonic band-gap structure in Si photonic-wire Bragg-grating

    Tomohiro Kita, Hirohito Yamada

    IEEE International Conference on Group IV Photonics GFP     133 - 135  2011年

     概要を見る

    We have systematically studied Bragg-grating filters in Si photonic-wire waveguides. We found an abnormal localized optical mode on the numerical calculations and verified it on the experimental measurements. This phenomenon originates from high index-contrast between the waveguide materials. Zero photonic band-gap structure was experimentally realized at transition structure of abnormal localized optical mode in 1-D photonic crystal. © 2011 IEEE.

    DOI

  • Optical crossing by hybrid Si-wire/silica waveguides

    Younosuke Wakayama, Tomohiro Kita, Hirohito Yamada

    IEEE International Conference on Group IV Photonics GFP     305 - 307  2011年

     概要を見る

    We are studying the feasibility of an integrated optical circuit consisting of Si-wire waveguides and silica-based waveguides. In order to realize such a hybrid waveguide optical circuit, we proposed a simple optical crossing structure consisting of heterogeneous waveguides, and investigated the characteristics by numerical analysis and measurement. We found that the insertion loss of the waveguide crossing is low enough, and it was largely improved by making crossing with Si-taper structure. © 2011 IEEE.

    DOI

  • Second and Third-Order Nonlinear Optical Effects in ZnO Channel Waveguides

    Tomohiro Kita, Yoshio Morales Teraoka, Yoshitomo Okawachi, Atsushi Tsukazaki, Masashi Kawasaki, Alexander L. Gaeta, Hirohito Yamada

    2011 CONFERENCE ON LASERS AND ELECTRO-OPTICS (CLEO)    2011年

     概要を見る

    We demonstrate simultaneous self-phase modulation and second harmonic generation in ZnO channel waveguides. We estimate a value of gamma = 13.9 +/- 3.0 W(-1)m(-1), indicating that ZnO offers promise as a platform for nonlinear devices. (C)2011 Optical Society of America

  • C-3-14 Si細線光導波路による波長可変レーザ用リング共振器フィルタの解析(導波路デバイス(1),C-3.光エレクトロニクス,一般セッション)

    鈴木 健, 北 智洋, 山崎 裕幸, 山田 博仁

    電子情報通信学会ソサイエティ大会講演論文集   2010 ( 1 ) 135 - 135  2010年08月

    CiNii

  • Self-phase modulation at visible wavelengths in nonlinear ZnO channel waveguides

    Edgar Yoshio Morales Teraoka, Daniel H. Broaddus, Tomohiro Kita, Atsushi Tsukazaki, Masashi Kawasaki, Alexander L. Gaeta, Hirohito Yamada

    APPLIED PHYSICS LETTERS   97 ( 7 )  2010年08月

     概要を見る

    We report the observation of nonlinear optical effects in the visible spectrum using ZnO channel waveguides. We demonstrate sixfold spectral broadening and a 2 pi phase shift due to self-phase modulation in ZnO channel waveguides using femtosecond optical pulses with a center wavelength of 840 nm. We measured a value for the nonlinear parameter gamma of 13.9 +/- 3.0 W-1 m(-1), which is more than 1300 times that of a highly nonlinear fiber. The calculated intensity-dependent refractive index is found to be consistent with previously reported values of bulk single-crystal ZnO. (C) 2010 American Institute of Physics. [doi: 10.1063/1.3480422]

    DOI

  • ZnO Channel Waveguides for Nonlinear Optical Applications

    Edgar Yoshio Morales Teraoka, Tomohiro Kita, Atsushi Tsukazaki, Masashi Kawasaki, Yasuo Ohtera, Hirohito Yamada

    JAPANESE JOURNAL OF APPLIED PHYSICS   49 ( 4 )  2010年

     概要を見る

    ZnO channel waveguides were fabricated for the first time, for the purpose of being used in nonlinear optical applications. Wide-bandgap ZnO was chosen for the core material to avoid two-photon absorption at wavelengths above 800nm which are used for biomedical applications. We calculated the single-mode conditions and group-velocity dispersion of the propagating modes for the waveguides. We also fabricated channel waveguides using single-crystal ZnO thin film grown on sapphire substrate. Measured propagation losses with a cut-back method were approximately 3 to 6 dB/mm for single-mode waveguides. (C) 2010 The Japan Society of Applied Physics

    DOI

  • Experimental and numerical analysis study of 1-D photonic crystal in Si photonic-wire waveguides

    Tomohiro Kita, Hirohito Yamada

    Proceedings of SPIE - The International Society for Optical Engineering   7606  2010年

     概要を見る

    We have systematically studied Bragg Grating Filters in Si photonic-wire waveguides. Highly uniform samples have been fabricated in a specialized foundry service for Si photonics. The reflected wavelength has been controlled over an 180 nm range. By changing the design parameters we controlled the photonic band-gap to be between 6 to 16 nm. Thermal tuning of the reflected wavelength was also measured, resulting in a wavelength shift of more than 3 nm. © 2010 Copyright SPIE - The International Society for Optical Engineering.

    DOI

  • Photonic band-gap anomaly in SOI photonic-wire Bragg-grating filter

    Tomohiro Kita, Ryota Ishikawa, Hirohito Yamada

    2010 7TH IEEE INTERNATIONAL CONFERENCE ON GROUP IV PHOTONICS (GFP)     237 - 239  2010年

     概要を見る

    We have systematically studied Bragg Grating Filters in Si photonic-wire waveguides. The reflected wavelength and the photonic band-gap were controlled over a wide range by changing the design parameters. We found a photonic band-gap anomaly on the numerical calculations and verified it on the experimental measurements. This phenomenon originates from the abnormal localized optical mode in 1-D photonic crystals.

    DOI

  • Practical integration method of active devices on SOI photonic integrated circuits.

    Tomohiro Kita, Masahiro Abe, Yasuo Ohtera, Hirohito Yamada

    2010 7TH IEEE INTERNATIONAL CONFERENCE ON GROUP IV PHOTONICS (GFP)     275 - 277  2010年

     概要を見る

    We propose a method of mounting LD chips on SOI substrate and discuss about the optical coupling loss between LDs and Si photonic-wire waveguides. In our scheme, light output from an LD is coupled to the optical waveguides through spot-size-converters (SSC). The simulations show that a minimum optical coupling loss of 1.6 dB and an offset tolerance of +/- 0.7 mu m for the LD chip positioning can be achieved. We measured the optical coupling loss, confirming the validity of the simulations.

    DOI

  • Si細線光導波路の曲がり損失の数値解析

    外間 洋平, 北 智洋, 大寺 康夫, 山田 博仁

    電子情報通信学会技術研究報告. OME, 有機エレクトロニクス   109 ( 283 ) 49 - 54  2009年11月

     概要を見る

    Si細線光導波路における曲げ損失を3つの損失要因に分解して考え,それら損失要因による損失の値を90度曲げ導波路,180度曲げ導波路,S字型導波路の3つの導波路パターンより算出することに成功した.従って,複数曲げを含む複雑な導波路パターンにおける全損失を,それら3つの損失要因の足し算によって求めることができ,従来の導波路における報告例との比較によって,その方法の妥当性を検証した.

    CiNii

  • SOI導波路基板上へのLDチップ実装方法に関する検討

    阿部 政浩, 宮村 悟史, 中村 幸治, 北 智洋, 大寺 康夫, 山田 博仁

    電子情報通信学会技術研究報告. OME, 有機エレクトロニクス   109 ( 283 ) 55 - 60  2009年11月

     概要を見る

    SOI光集積プラットフォーム上に,半導体レーザ(LD)やフォトダイオード(PD)を集積化する技術が求められている.本論文では,SOI光集積プラットフォーム上へのLDの実装方法およびSi細線光導波路とLDとの低損失結合方法について理論的および実験的に検討した.検討した構造としては,LDをSOI光集積プラットフォーム上へフリップチップ実装し,スポットサイズ変換器を設けたSi細線光導波路とButt-joint結合させる方法である.解析では,2dB程度の最小光結合損失が得られることが分かり,光結合損失の測定結果と比較することで,解析の妥当性を示す.また,チップ実装時の位置ずれに対しても,十分なトレランスを有することが分かった.

    CiNii

  • ZnO/MgZnO界面における量子ホール効果

    塚崎 敦, 大友 明, 北 智洋, 大野 裕三, 大野 英男

    固体物理   499 ( 42 ) 559 - 567  2007年09月

    記事・総説・解説・論説等(学術雑誌)  

    CiNii

  • ZnOの量子ホール効果

    大友明, 塚崎敦, 北智洋, 大野裕三, 大野英男, 川崎雅司

    応用電子物性分科会誌   13 ( 2 ) 73 - 78  2007年02月

    記事・総説・解説・論説等(その他)  

  • (In,Ga)As gated-vertical quantum dot with an Al2O3 insulator

    T. Kita, D. Chiba, Y. Ohno, H. Ohno

    APPLIED PHYSICS LETTERS   90 ( 6 )  2007年02月

     概要を見る

    The authors fabricated a gated-vertical (In,Ga)As quantum dot with an Al2O3 gate insulator deposited using atomic layer deposition and investigated its electrical transport properties at low temperatures. The gate voltage dependence of the dI/dV-V characteristics shows clear Coulomb diamonds at 1.1 K. The metal-insulator gate structure allowed the authors to control the number of electrons in the quantum dot from 0 to a large number estimated to be about 130. (c) 2007 American Institute of Physics.

    DOI

  • Bias voltage dependence of the electron spin injection studied in a three-terminal device based on a (Ga,Mn) As/ n+-GaAs Esaki diode

    M. Kohda, T. Kita, T. Kita, Y. Ohno, Y. Ohno, F. Matsukura, F. Matsukura, H. Ohno, H. Ohno

    Applied Physics Letters   89  2006年07月

     概要を見る

    We investigated injection of spin polarized electrons in a (Ga,Mn)As/n+-GaAs Esaki diode (ED) by using a three-terminal device integrating a (Ga,Mn)As ED and a light emitting diode (LED). Electroluminescence polarization (PEL) from the LED was measured under the Faraday configuration as a function of bias voltages applied independently to the Esaki diode and to the LED. The maximum PELof 32.4% was observed when the valence electrons near the Fermi energy of (Ga,Mn)As are ballistically injected into the LED. © 2006 American Institute of Physics.

    DOI

  • Pulse-width and magnetic-field dependences of current-induced magnetization switching in a (Ga,Mn)As magnetic tunnel junction

    D. Chiba, T. Kita, F. Matsukura, H. Ohno

    Journal of Applied Physics   99  2006年05月

     概要を見る

    We have investigated the pulse-width and magnetic-field dependences of current-induced magnetization switching in a (Ga,Mn) AsGaAs (Ga,Mn) As magnetic tunnel junction. Critical current to induce magnetization switching shows a linear dependence on pulse width from 10 to 1000 μs. The magnetic-field dependence appears to indicate that the observed current-induced magnetization switching proceeds through metastable magnetization structures. © 2006 American Institute of Physics.

    DOI

  • Observation of e2/h conductance steps in a side-gate point contact on In<inf>0.75</inf>Ga<inf>0.25</inf>As/In<inf>0.75</inf>Al<inf>0.25</inf>As heterostructure

    T. Kita, S. Gozu, Y. Sato, S. Yamada

    Journal of Superconductivity and Novel Magnetism   16   327 - 329  2003年12月

     概要を見る

    In 1996, it was suggested by K. J. Thomas et al. (Phys. Rev. Lett. 77,135 (1996)) that 0.7(2e2/h) conductance structure in Quasi-1 DEG (Q1DEG) at GaAs/AlGaAs heterostructure might be related to spin polarization at zero magnetic field. We have recently studied spontaneous spin-splitting in the 2DEGs formed at normal metamorphic In0.75Ga0.25As/n0.75Al0.25As heterojunctions grown on GaAs substrates and obtained the value of ≲10 meV as the zero-field splitting at Fermi level (Y. Sato et al., J. Appl. Phys. 89, 8017 (2001)). In this work, we attempted to observe spin-related phenomena in this heterojunction Q1DEGs at zero magnetic field. We observed e2/h conductance steps in low electron concentration side-gate point contact. © 2003 Plenum Publishing Corporation.

  • 20pTL-3 高 In 組成 InGaAs/InAlAs 拡散的細線における Rashba effect

    掛川 智康, 北 智洋, 赤堀 誠志, 山田 省二

    日本物理学会講演概要集   58 ( 2 ) 575 - 575  2003年08月

    CiNii

  • Spontaneous spin-splitting observed in resonant tunneling diode with narrow band-gap asymmetric quantum well

    S Yamada, T Kikutani, S Gozu, Y Sato, T Kita

    PHYSICA E-LOW-DIMENSIONAL SYSTEMS & NANOSTRUCTURES   13 ( 2-4 ) 815 - 818  2002年03月

     概要を見る

    This paper deals with the experiments to observe the spontaneous spin-splitting (SSS) in the resonant tunneling diode (RTD), which was specially designed to have a narrow band gap as well as an asymmetric potential well. In current-voltage (I-V) characteristics. there observed a current peak doubly splitted (denoted as P1-1 and P1-2) at low bias field. The difference of the derivative peak height of P1-1 between those with and without the parallel magnetic field (dI/dV(B)-dI/dV(B = 0)), which was applied along the easy axis of the emitter electrode. increased with increasing field strength, while the quantity of P1-2 stayed almost zero, The increase of the difference of the derivative peak height of P1-1 was found to saturate almost at the coercive field of the electrode. It was also found that those variations of the derivative peak height were observed only in the case of electron injection via the ferromagnetic (NiFe) emitter electrode. The amount of splitting (similar to 15 meV) observed was almost the same as those estimated from magnetoresistance measurements. These results suggest that the observed splitted peak is intimately related to the SSS expected at the center well in our unique RTDs. (C) 2002 Elsevier Science B.V. All rights reserved.

    DOI

  • Study for realization of spin-polarized field effect transistor in In0.75Ga0.25As/In0.75Al0.25As heterostructure

    Y Sato, S Gozu, T Kita, S Yamada

    PHYSICA E-LOW-DIMENSIONAL SYSTEMS & NANOSTRUCTURES   12 ( 1-4 ) 399 - 402  2002年01月

     概要を見る

    For realization of the spin-polarized field effect transistor (spin-FET), we investigated a gated modulation of spin-orbit interaction and a spin-injection from a ferromagnetic metal (FM) to a two-dimensional electron gas (2DEG). Prepared samples were an In0.75GaO0.25As/In0.75Al0.25As modulation-doped narrow-gap heterojunction grown by molecular beam epitaxy (MBE). For the determination of spin-orbit interaction parameter, alpha we measured Shubnikov-de Haas (SdH) oscillations at 1.5 K. We confirmed a modulation of D when a gate voltage was applied. We also carried out spin-injection experiments using a multi-terminal geometry sample, which had two different widths Ni40Fe60 electrodes. We observed a spin-valve like effect in a source-drain resistance of similar to 0.1% as well as a resistance hysteresis behavior of similar to 12% in non-local geometry below 20 K. These results are the first step to realize an active spintronic device, such as spin-FET. (C) 2002 Elsevier Science B.V. All rights reserved.

    DOI

  • Ballistic spin transport in four-terminal NiFe/In(0.7)5Ga(0.25)As structure

    Y Sato, S Gozu, T Kita, S Yamada

    JAPANESE JOURNAL OF APPLIED PHYSICS PART 2-LETTERS   40 ( 10B ) L1093 - L1096  2001年10月

     概要を見る

    Spin-injection experiments in NiFe/two-dimensional electron gas (2DEG)/NiFe four-terminal devices are described. The 2DEG was confined at a modulation-doped In0.75Ga0.25As/In0.75Al0.25As heterojunction interface. NiFe source-drain electrodes were located similar to1 mum apart and two voltage probes were fabricated between them. The separation between the NiFe electrodes was thus almost less than both the mean free path (similar to2 mum) and the spin-diffusion length (&gt; 1 mum) of the 2DEG. In nonlocal four-terminal measurements, where a constant current (i) was sent through one NiFe to one ohmic electrode, the two-terminal magnetoresistance (R-2t = exhibited a spin-valve-like effect, while R-4t = V-4t/i showed a resistance hysteresis. The amplitude of the latter amounted to almost 12% of the R-4t (B = 0) at 1.5 K, the extent of which was one order of magnitude larger than those so far reported. These results suggest the importance of a quasi-ballistic as well as a spin-coherent coupling between the two NiFe electrodes, which may crucial in the future operation of spin field-effect transistors (FETs).

  • Characterization of high indium content metamorphic InGaAs/InAlAs modulation-doped heterostructures

    S Gozu, T Kita, Y Sato, S Yamada, M Tomizawa

    JOURNAL OF CRYSTAL GROWTH   227   155 - 160  2001年07月

     概要を見る

    We have studied electronic and structural characterizations of high indium content metamorphic InGaAs/InAlAs modulation-doped heterostructures. An improved low-temperature electron mobility of mu (e) = 5.45 x 10(5) cm(2) Vs in [(1) over bar 1 0] was confirmed for a directed Hall-bar sample when Si-doped InAlAs layer was slightly etched. In addition, inplane mobility anisotropy of 40% between [(1) over bar 1 0] and [1 1 0] directions. We confirmed. This anisotropy seems to br originated fi om the different undulation period between[(1) over bar 1 0] and [1 1 0] directions. We theoretically calculated electron mobility taking both alloy disorder scattering and background impurity scattering into account. It is found that the calculated and experimental values are in good agreement. (C) 2001 Elsevier Science B.V. All rights reserved.

    DOI

  • Large spontaneous spin splitting in gate-controlled two-dimensional electron gases at normal In0.75Ga0.25As/In0.75Al0.25As heterojunctions

    Y Sato, T Kita, S Gozu, S Yamada

    JOURNAL OF APPLIED PHYSICS   89 ( 12 ) 8017 - 8021  2001年06月

     概要を見る

    Amounts of spontaneous spin splittings were estimated from low-temperature magnetoresistances in two-dimensional electron gases created at In0.75Ga0.25As/In0.75Al0.25As heterojunctions under a gate bias. Typical sheet electron densities and mobilities in the raw wafers were similar to1.0 x 10(12)/cm(2) and 2-5 x 10(5) cm(2)/V s at 1.5 K, respectively. A maximum spin-orbit coupling constant alpha (zero) of similar to 30(x10(-12) eV m) was obtained for the van der Pauw sample. In gated Hall-bar samples, a decrease in the alpha (zero) value with decreasing gate voltage (V-g) was first confirmed in a normal heterojunction. The main origin for such a large alpha (zero), which is a few times larger than any previously reported, was found to be a structure-dependent so-called interface contribution in the Rashba term. (C) 2001 American Institute of Physics.

    DOI

  • An investigation of tunable spin-orbit interactions in front-gated In0.75Ga0.25As/In0.75Al0.25As heterojunctions

    Y Sato, S Gozu, T Kita, S Yamada

    PHYSICA E-LOW-DIMENSIONAL SYSTEMS & NANOSTRUCTURES   10 ( 1-3 ) 77 - 80  2001年05月

     概要を見る

    We investigated zero-field spin-splitting in normal-type In0.75Ga0.25As/In0.75Al0.25As heterostructure by magnetoresistance measurements at 1.5 K. The maximum value of spin-orbit interaction parameter, alpha (zero) obtained here is 32x10(-12) eVm. We also confirmed a tuning of alpha (zero) by applying gate biases. On the other hand, we observed no beat oscillation when the In0.75Ga0.25As well width decreased from 30 to 10nm. These results suggested that interface contribution related to the asymmetry of wave function penetration into the barriers could be enhanced in our heterojunction (C) 2001 Published by Elsevier Science B.V.

    DOI

  • Large spontaneous spin-splitting and enhanced effective g-factor in two-dimensional electron gases at In0.75Ga0.25As/In0.75Al0.25As metamorphic heterojunctions

    T Kita, Y Sato, S Gozu, S Yamada

    PHYSICA B   298 ( 1-4 ) 65 - 69  2001年04月

     概要を見る

    We have estimated spin-splitting energy of two-dimensional electron gases formed at metamorphic In0.75Ga0.25As/In0.75Al0.25As heterojunctions by analyzing magneto-resistance traces up to 10 T. This heterojunction often reveals a large spontaneous spin-splitting at low fields, while at high fields, Zeeman splitting becomes dominant. We have investigated and compared the two sanples; one reveals beating oscillation and hence has a spontaneous or zero-field spin-splitting and another does not. In the former sample, if we assume the equal sign for both the spin-splittings, the dependency of the absolute splitting energy on the magnetic field is found to have a minimum (Delta = 2 meV) at about 3.5 T, in which we also confirmed a zero-field spin-splitting of Delta (0) = 11.04meV and very much enhanced g* = - 42.0 at 1.5 T. In contrast, effective g-factor (g*) obtained at high fields in the latter sample is g* = - 7.7 at 1.5 T, which is fairly smaller than that in the former. Origins of those features are discussed and the possibility of linear spin-splitting dependency on magnetic field is pointed out. (C) 2001 Published by Elsevier Science B.V.

    DOI

  • Effect of strain relaxation layers in high Indium content metamorphic InGaAs/InAlAs modulation doped heterostructures

    S Gozu, T Kita, H Sato, S Yamada

    2001 INTERNATIONAL CONFERENCE ON INDIUM PHOSPHIDE AND RELATED MATERIALS, CONFERENCE PROCEEDINGS     55 - 58  2001年

     概要を見る

    We have investigated effect of residual strain appeared in the transport and optical properties of high indium content metamorphic In0.75Ga0.25As/In0.75Al0.25As modulation doped heterostructures grown via (inverse step: IS-) step graded buffer (SGB). The effect of residual strain was controlled by IS structure and a drastic decrease of residual strain (about one third) was observed. We have also observed an improved low temperature (77K) electron mobility, when the IS buffer was used. We found that the residual strain is one of the important interface condition which determines the low temperature (77K) electron mobility.

    DOI

  • Critical layer thickness study in In0.75Ga0.25As/In0.5Al0.5As pseudomorphic resonant tunneling diode structure grown on GaAs substrates

    Shin-Ichiro Gozu, Tomohiro Kita, Tomoyuki Kikutani, Syoji Yamada

    Journal of Crystal Growth   227 ( 228 ) 161 - 166  2001年

     概要を見る

    We have studied critical layer thickness (CLT) in an In0.75Ga0.25As resonant tunneling diode structure grown on a GaAs substrate via an InAlAs step-graded buffer (SGB) with two types of inverse step(IS)-SGB. We have observed red or blue shift in photoluminescence spectra and CLT change depending on SGB condition. This change reflects from the difference of residual strain InAlAs SGBs adopted here. © 2001 Elsevier Science B.V.

    DOI

▼全件表示

その他

  • 高い環境耐性を有するキャリアコンバータ技術の研究開発

    2016年05月
     
     

     概要を見る

    5G時代に対応した大容量・低遅延・シームレスな光/ミリ波変換デバイ
    スの開発と実証評価

  • ナノハイブリッド電気光学ポリマーを用いた光インターコネクト技術

    2016年04月
     
     

     概要を見る

    本課題では、電気光学ポリマーとシリコン光導波路を複合化する事で、これまでにない機能性を有する導波路デバイスを作製する。本研究の目的は、車載通信に用いるインターコネクトデバイスへの製品化を目的として高機能・小型光導波路を作製する。

  • 狭線幅波長可変レーザの開発

    2015年12月
     
     

     概要を見る

    次世代の大容量光通信方式として実用化の始まっているデジタル・コヒーレント光通信用狭線幅波長可変レーザーをシリコンフォトニクスによって独自に開発した超小型波長可変フィルターを用いて実現する。波長可変動作、狭線幅発振といった個々の特性に関しては、すでに十分な特性が得られているが本技術が実用化に耐えうる特性を持つことを証明するために高出力、省スペース、安定した波長可変動作といった特性を満足する波長可変レーザーモジュールを開発する。

  • シリコンフォトニック波長可変レーザを用いた医療イメージング用光源の開発

    2015年04月
     
     

     概要を見る

    光断層イメージングに必要な広波長帯域可変レーザをシリコンフォトニクスを用いて作製した波長可変フィルタと量子ドット光増幅器を用いて実現する。

  • 大容量光通信用高機能シリコンフォトニック波長可変レーザの開発

    2014年08月
     
     

     概要を見る

    次世代の大容量光通信技術であるデジタル・コヒーレント光通信、フォトニックネットワーク、超広周波数帯域波長分割多重といった通信方式において使用できる実用的な特性を持つ高機能波長可変レーザをシリコンフォトニクスを用いて開発する。

  • ナノハイブリッド電気光学ポリマーを用いた光インターコネクト技術

    2014年04月
     
     

     概要を見る

    本課題では、電気光学ポリマーとシリコン光導波路を複合化する事で、これまでにない機能性を有する導波路デバイスを作製する。本研究の目的は、車載通信に用いるインターコネクトデバイスへの製品化を目的として高機能・小型光導波路を作製する。

  • 次世代コヒーレント光通信用 超小型・狭線幅シリコンフォトニクス波長可変レーザモジュールの開発

    2014年02月
     
     

     概要を見る

    次世代の大容量光通信方式として実用化の始まっているデジタル・コヒーレント光通信用狭線幅波長可変レーザーをシリコンフォトニクスによって独自に開発した超小型波長可変フィルターを用いて実現する。波長可変動作、狭線幅発振といった個々の特性に関しては、すでに十分な特性が得られているが本技術が実用化に耐えうる特性を持つことを証明するために高出力、省スペース、安定した波長可変動作といった特性を満足する波長可変レーザーモジュールを開発する。

  • シリコンフォトニクスを用いたデジタル・コヒーレント光通信用波長可変レーザの開発

    2012年12月
     
     

     概要を見る

    本波長可変レーザは、すでに波長可変幅、狭線幅動作に関しては十分な特性を示しており、素子の安定性を向上させ出力光強度を大きくできれば技術移転が可能である。本研究によってシリコン細線光導波路チップへのSOAのフリップチップ実装技術や反射戻り光低減のためのスポットサイズコンバータの構造最適化手法などを開発し、実システムで使用可能出力光強度を得る事を目標とする。

  • 局所レーザー加熱を用いたSi細線光導波路デバイスのトリミング技術の開発

    2011年09月
     
     

     概要を見る

    Siをコア、SiO2をクラッドとして用いる超High-ΔのSi細線光導波路は、シリカ系の光導波路で作製されてきた従来の光回路を大幅に小型・低消費電力化できるため、通信用光デバイスやLSIチップ内光配線、バイオセンシングなどの各種センサーといった広範な領域で様々な応用デバイスの実現を期待されている。このように様々な分野で活発な研究が行われているにも関わらず、Si光導波路デバイスは未だあまり実用化されていない。この実用化にあたっての最大の障壁は、僅かな製造誤差によって特性が大きくばらつくことにある。Si細線導波路デバイスのサイズは極めて小さい(マッハ・ツェンダー干渉計型熱光学光スイッチでも100μm以下)ために、数nm程度の製造誤差でも光共振器や光干渉計等を有するデバイス特性には大きな影響がでてしまう。本研究ではこの問題を解決するために、光導波路をアモルファスSiによって形成し、局所的なレーザー照射によってアモルファスSiの光導波路コアの一部分を加熱し、部分的に多結晶Siを析出させることで屈折率を変化させデバイス特性をトリミングする技術を開発する。

  • 省電力ネットワーク実現のためのスロット型Si細線光導波路の機能集積化の研究

    2009年07月
     
     

     概要を見る

    Si細線を用いた光導波路によって構成される光集積回路は、現行のシステムを大幅に小型化、低消費電力化することが期待されている。本研究ではSi細線にスロット型光導波路を導入することで更なる高機能化を図る。

  • Si光導波路の界面化学反応を利用した機能性光学デバイスの研究

    2009年04月
     
     

     概要を見る

    本研究課題では、近年発展が著しいSiをベースとした光学デバイス(Siフォトニクス)の研究に、従来は用いられなかった電気化学的な手法を応用する。Siフォトニクスの持つ可能性と電気化学において蓄積された材料物性制御技術を融合することで、より高機能・低消費電力なデバイス応用を可能にする微小領域の光波制御手法を提案、実証していく。

▼全件表示

受賞

  • 石田實記念財団研究奨励賞

    2014年11月   石田寛記念財団   大容量光通信用シリコンフォトニック波長可変レーザに関する研究  

  • 第23回応用物理学会 講演奨励賞

    2007年10月   応用物理学会  

講演・口頭発表等

  • シリコンフォトニクスチップを外部共振器とした機能性レーザの開発

    電子情報通信学会  

    発表年月: 2017年09月

  • Heterogeneous Lasers with Silicon Photonic External Cavity

    Tomohiro Kita, Shotaro Takei, Atsushi Matsumoto, Naokatsu Yamamoto, Hirohito Yamada

    応用物理学会ーOSA joint symposia  

    発表年月: 2017年09月

  • Silicon Photonic Wavelength Tunable Lasers for high-capacity optical communication system

    Optical Fiber Communication Conference and Exhibition (OFC) 2017   (アメリカ合衆国 Los Angeles) 

    発表年月: 2017年03月

  • Heterogeneous silicon photonic wavelength tunable laser diodes

    The 6th Annual World Congress of Nano Science and Technology-2016(Nano S&T-2016)   (シンガポール) 

    発表年月: 2016年10月

  • Ultra-compact Wavelength Tunable Quantum Dot Laser with Silicon Photonic External Cavity

    Tomohiro Kita, Naokatsu Yamamoto, Tetsuya Kawanishi, Hirohito Yamada

    The Conference on Lasers and Electro-Optics(CLEO)   (アメリカ合衆国 サンノゼ) 

    発表年月: 2015年05月

  • InAs 量子ドット光増幅器を用いた1.2μm 帯シリコンフォトニック波長可変レーザ

    北 智洋, 山本 直克, 川西 哲也, 山田 博仁

    第62回応用物理学会春季学術講演会   (平塚) 

    発表年月: 2015年03月

  • TiO2微粒子ポリマを用いたシリコン細線光導波路のアサーマル化

    第62回応用物理学会春季学術講演会   (平塚市) 

    発表年月: 2015年03月

  • ハイブリッド集積シコンフォトニクスリングフィルタ外部共振器型波長可変レーザの狭線幅及び高出力特性

    佐藤 健二, 小林 直樹, 波若 雅彦, 山本 圭介, 渡邊 真也, 北 智洋, 山田 博仁, 山崎 裕幸

    電子情報通信学会 OPE12月研究会  

    発表年月: 2014年12月

  • Silicon Photonic Devices for a Large Capacity Optical Communication system

    Tomohiro Kita, Tang Rui, Munetoshi Soma, Hirohito Yamada

    The 4th International Symposium on Photonics and Electronics Convergence   (日本国 東京) 

    発表年月: 2014年11月

  • ATHERMAL SILICON PHOTONIC DEVICES USING HYBRID POLYMER CLADDING

    Freddy Susanto Tan, Okihiro Sugihara, Hirohito Yamada, Toshikuni Kaino

    The 23rd International Conference on Plastic OpticalFiber   (日本国 日吉) 

    発表年月: 2014年10月

  • RECENT PROGRESS OF OPTICAL INTERCONNECT DEVICES USING PHOTONIC POLYMERS

    Sugihara, T. Kita, D. Inoue, F. S. Tan, A. Hattori, A. Kawasaki, M. Sato, T. Yamashita, M. Mizuno, S. Okada, M. Kagami, M.Tsuchimori, O. Watanabe, H. Yamada, T. Kaino

    The 23rd International Conference on Plastic Optical Fibers   (日本国 日吉) 

    発表年月: 2014年10月

  • 高出力シリコンフォトニック波長可変レーザ

    唐 睿, 山田博仁

    電子情報通信学会2014年ソサイエティ大会   (日本国 徳島) 

    発表年月: 2014年09月

  • 広波長可変帯域を持つシリコンフォトニックレーザ

    唐 睿, 山田 博仁

    第75回応用物理学秋季学術講演会   (日本国 札幌) 

    発表年月: 2014年09月

  • 1.Wide-band Wavelength Tunable Laser Diode with Si Photonic Filter

    Tang Rui, Hirohito Yamada

    IEEE International Conference of Semiconductor Laser   (スペイン パルマ) 

    発表年月: 2014年09月

  • 3. Si Photonic Wavelength Tunable Laser Diode with the Phase Shifter of Longitudinal Mode

    Tang Rui, Hirohito Yamada

    IEEE Group ⅣPhotonics   (フランス パリ) 

    発表年月: 2014年08月

  • 狭線幅シリコンフォトニック波長可変レーザモジュール

    唐 睿, 山田博仁

    電子情報通信学会LQE研究会   (日本国 小樽) 

    発表年月: 2014年08月

  • 高非線形TiO2光導波路による広波長帯域光発生

    内島晃司, 藪野正裕, 逢坂 崇, 片山竜二, 枝松圭一, 山田博仁

    電子情報通信学会LQE研究会   (日本国 東京) 

    発表年月: 2014年06月

  • デジタルコヒーレント通信用シリコンフォトニック波長可変レーザ

    フォトニックデバイス・応用技術研究会   (日本国 東京) 

    発表年月: 2014年05月

  • シリコンフォトニック波長可変レーザ

    唐 睿, 根本景太, 山田博仁

    電子情報通信学会2014年総合大会   (日本国 新潟) 

    発表年月: 2014年03月

▼全件表示

学内研究費(特定課題)

  • ハイブリッドレーザを用いたFMCW測距技術の開発

    2021年  

     概要を見る

    シリコンフォトニクスチップ波長可変フィルタと化合物半導体光増幅器を結合したハイブリッド波長可変レーザを用いて、FMCW(Frequency modulated continuous wave)方式により距離計測を技術を開発した。高速な周波数変調が可能な電流注入型熱光学式位相シフタの利用によって、25 KHzの変調周波数で2.5 cm以下の距離精度を実証した。

  • 1チップレーザービームスキャナの作製

    2020年  

     概要を見る

    経路差を用いたシリコンアレイ導波路及びブラッグ回折格子構造によってレーザ光の波長によってレーザビームの出射方向を二次元的に制御できることを確認した。さらに光増幅チップとシリコンフォトニクスチップとを光学接着剤を用いて結合し良好なレーザ発振特性が得られた。これらの成果によって1チップ二次元ビームスキャナ実現への道筋を得ることができた。

  • 光波制御ユニットの高精度制御に関する研究

    2019年  

     概要を見る

    シリコンフォトニクスチップ上に試作した多数のヒーターを同時に制御する計測システムを構築した。複数の直流安定化電源、ファンクションジェネレータ等を独立に制御することでハイブリッドレーザーから出力した二波長のレーザー光を用いてマイクロ波を発生させることに成功した。

  • 非常に広い可変波長域を有するヘテロジニアス波長可変レーザの開発

    2018年  

     概要を見る

    シリコンフォトニクスによって作製した外部共振器と化合物半導体光増幅器とを組み合わせたヘテロジニアス波長可変レーザをより広い波長範囲に適用するために波長依存性の小さな導波路型波長可変フィルタを開発した。本研究においては、リング共振器とバス導波路とを結合する方向性結合器に曲がり導波路構造を用いることで、従来型の波長可変フィルタの1.5倍程度の波長可変範囲で使用可能な波長フィルタの設計、試作した。方向性結合の結合効率の波長依存性が小さいためリング共振器のQ値といった特性の波長依存性が低減されることが確認できた。

 

現在担当している科目

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委員歴

  • 2014年12月
    -
    継続中

    電子情報通信学会シリコンフォトニクス時限研究専門委員会  専門委員

  • 2014年12月
    -
    継続中

    電子情報通信学会シリコンフォトニクス時限研究専門委員会  専門委員

  • 2016年06月
    -
    2019年05月

    電子情報通信学会  和文論文誌C編集委員

  • 2016年06月
    -
    2019年05月

    電子情報通信学会  和文論文誌C編集委員

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    電波タイムズ  

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    日経産業新聞  

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