Kyushu University Academic Staff Educational and Research Activities Database
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Kazutoshi Kato Last modified date:2018.06.28



Graduate School


Academic Degree
Dr. Engineering
Field of Specialization
Integrated optoelectronics system
Outline Activities
Research: coraborative research on "Tunable laser system for ultra-wide band optical communications" with a Japanese company, "High speed optical wavelength converter for ultra-wide band optical communications","Ultra-high repition terahertz pulse generation", "Phase shift technology for ultra-high repition electromagnetic pulse" supported by Grants-in-Aid for Scientific Research, "Teraherz 100Gbit/s real-tme wireless transmission" supported by the Strategic Information and Communications R&D Promotion Programme (SCOPE) , from the Ministry of Internal Affairs and Communications, Japan, and "Break through for terahertz gap using large-scale monolithic photonics integration" supported by JST.
Education: Lecture of "Material science I" for 2nd-degree of undergraduate students "Electromagnetic wave enginering I" for 3rd-degree of undergraduate students and "High-frequency devices" for 1st-degree master course students, Superviser of 4th-degree of undergraduate students' graduation theses, master course students' theses, and doctral course students' theses.
Social activities: Chairperson of Optoelectronics committee, Member of Microwave photonics committee, Member of Microoptics research group and Editing chairperson of IEICE ES journal (Japanese edition).
Research
Research Interests
  • Ultra-high repitition terahertz pulse generation
    keyword : ultra-high repitition, terahertz pulse
    2017.04~2020.03.
  • Teraherz-wave large capacity wireless transmission
    keyword : Teraherz-wave, wireless transmission
    2013.10~2016.03.
  • controll of semiconductor laser diode for ultrawide-band optical communication
    high-speed wavelength converter for ultrawide-band optical communication
    keyword : optoelectronics, semiconductor laser, optical communication
    2012.04~2015.03.
Academic Activities
Papers
1. Shota Takeuchi, Kazuki Sakuma, Kazutoshi Kato, Yasuyuki Yoshimizu, Yu Yasuda, Shintaro Hisatake, Tadao Nagatsuma, Novel Lightwave-Interferometric Phase Detection for Phase Stabilization of Two-Tone Coherent Millimeter-Wave/Microwave Carrier Generation, IEICE Trans. Electron., Vol. E99-C, 1048-1054, 2016.09, For phase stabilization of two-tone coherent millimeter-wave/microwave carrier generation, two types of phase detection schemes were devised based on lightwave interferometric technique, the Mach-Zehnder interferometric method and the pseudo Mach-Zehnder interferometric method. The former system showed clear eye patterns at both OOK and PSK modulations of 1 Gbit/s on the 12.5-GHz carrier. The latter system demonstrated the error-free transmission at OOK modulation of 11 Gbit/s on the 100-GHz carrier..
2. Ryoga Kimura, Yudai Tatsumoto, Kazuki Sakuma, Hirokazu Onji, Makoto Shimokozono, Hiroyuki Ishii, Kazutoshi Kato, Sub-microsecond wavelength stabilization of tunable lasers with the internal wavelength locker, Jpn. J. Appl. Phys., Vol. 55, 2016.07, We proposed a method of accelerating the wavelength stabilization after wavelength switching of the Tunable Distributed Amplification (TDA-) DFB laser using the internal wavelength locker to reduce the size and the cost of wavelength control system. The configuration of the wavelength stabilization system based on this locker was as follows. At the wavelength locker, the light intensity after an optical filter is detected as a current by the photodiodes (PDs). Then, for estimating the wavelength, the current is processed by the current/voltage-converting circuit (IVC), logarithm amplifier (Log Amp) and Field Programmable Gate Array (FPGA). Finally, the laser current is controlled to tune to the desired wavelength with reference to the estimated wavelength. With this control system the wavelength is stabilized within 800 ns after wavelength switching which is even faster than that with the conventional control system..
3. Jun Tsuboi, Takeshi Kuboki, Kazutoshi Kato, Wide-capture-range, high-precision wavelength stabilization within ±50 MHz for flexible-grid wavelength division multiplexing by photomixing technique, Jpn. J. Appl. Phys., Vol. 55, 2016.07, The lasers for the flexible-grid wavelength division multiplexing (WDM) system are required to have high precision of wavelength stability. Previously, we proposed the wavelength-controlling system of the Distributed FeedBack Laser Diode (DFB-LD) with the photomixing technique and a microwave filter to precisely measure the optical frequency error from the target value. To enlarge the wavelength-capture range, we improve the system to detect the wavelength error with two different microwave filters in parallel. Experimental results show that the wavelength-capture range is extended up to 4 GHz while the wavelength error is still kept within ±50 MHz..
4. Hirokazu Onji, Shota Takeuchi, Yudai Tatsumoto, Nobuhiro Nunoya, Makoto Shimokozono, Hiroyuki Ishii, Kazutoshi Kato, Fast wavelength switching with tunable distributed amplification distributed feedback laser by feedforward control technique, Jpn. J. Appl. Phys., Vol. 53, 2014.07, We proposed the way to accelerate the wavelength switching at the TDA-DFB laser based on the feedforward control. From experimental lasers’ responses, we designed and simulated the feedforward controllers using MATLAB/Simulink so as to reduce the time for wavelength stabilization. We applied this technique to two different situations; one is for the laser drive circuit with a large output current and 50-ns rise time, and the other is for that with a moderate output current and 5-ns rise time. In both situations, we showed the improvement of the wavelength switching times which were from 450 ns to 150 ns and 75 ns to 35 ns, respectively. From these results, it is confirmed that the proposed control technique is efficient for possible practical applications..
Presentations
1. 春木 隼, 坂野 豪紀, 佐熊 一輝, 加藤 和利, 犬伏 祐樹, 藤田 悠介, 久武 信太郎, 永妻 忠夫, First demonstration of 300-GHz band wireless transmission with arrayed photomixer, 2016年電子情報通信学会ソサイエティ大会, 2016.10.
2. 坪井 淳, Takeshi Kuboki, Kazutoshi Kato, Optical frequency stabilization within ±20MHz of distributed feedback laser controlled by novel feedback
algorithm, 21st Microoptics Conference, 2016.10.
3. 春木 隼, 坂野 豪紀, 佐熊 一輝, 加藤 和利, 犬伏 祐樹, 藤田 悠介, 久武 信太郎, 永妻 忠夫, First demonstration of 300-GHz band wireless transmission with arrayed photomixer, 21st Microoptics Conference, 2016.10.
4. 木村 凌河, 立本 雄大, 恩地 裕和, Takeshi Kuboki, Kazutoshi Kato, Internal-wavelength-locker based feedforward/feedback co-operative wavelength control for 100 ns wavelength switching, 21st Microoptics Conference, 2016.10.
5. 藤村 勇起, 中村 諒平, Takeshi Kuboki, Kazutoshi Kato, Wavelength Selective Filter Based Mach-Zernder Interferometric Phase Stabilization for High-Frequency Carrier Generation, 21st Microoptics Conference, 2016.10.
6. キム ヨンジン, 加藤 和利, Optical Design of Evanescently Coupled Photodiode for Terahertz Wave Generation, 平成28年度電機・情報関係学会九州支部連合大会国際セッション, 2016.09.
7. 坂野 豪紀, 春木 隼, 佐熊 一輝, 加藤 和利, 4-Channel Synchronous THz-wave Generator Compoased of Arrayed UTC-PDs and Antennas, OECC/PS 2016, 2016.07.
8. 山中 友輔, 藤村 勇起, 加藤 和利, Demonstration of Controlling Chromatic Dispersion at SOA with Mach-Zehnder Interferometric Measurement System, OECC/PS 2016, 2016.07.
9. Kazuki Sakuma, Yuki Fjimura, Shota Takeuchi, Kazutoshi Kato, Shintaro Hisatake, Tadao Nagatsuma, Coherent THz Power Combiner Consisting of Arrayed Uni-Traveling Carrier Photodiodes  and Planar Lightwave Circuit, SPIE Photonics West 2016, 2016.02.
10. Ryoga Kimura, Yudai Tatsumoto, Kazuki Sakuma, Hitrokazu Onji, Makoto Shimokozono, Hiroyuki Ishii, Fast Wavelength Stabilization of Tunable Lasers with the Internal Wavelength Locker, 20th Microoptics Conference (MOC’15), 2015.10, [URL], The wavelength control system with the internal wavelength locker of the tunable lasers is configured so as to accelerate the wavelength detection speed. With this control system the wavelength is stabilized within 3.8 µs after wavelength switching which is even faster than that with the conventional control system..
11. Jun Haruki, Kazuki Sakuma, Kazutoshi Kato, SYNCHRONOUS THZ WAVE COMBINER CONSISTING OF ARRAYED PHOTOMIXERS, 20th Microoptics Conference (MOC’15), 2015.10, [URL], We propose a power combiner of the synchronous terahertz waves for generating a higher coherent terahertz output power. The combiner consists of arrayed photomixers with bowtie-antennas. The experimental results show terahertz waves synchronized by the combiner results sum of the powers from photomixers and the directional gain of about 2 dB..
12. Jun Tsuboi, Takeshi Kuboki, Kazutoshi Kato, WAVELENGTH STABILIZATION WITHIN 0.05 GHz WITH PHOTOMIXING TECHNIQUE AND LASER CURRENT CONTROLLING, 20th Microoptics Conference (MOC’15), 2015.10, The lasers for the WDM system with the flexible grid need to have highly accurate wavelength tuning and stability. Insteadof using optical filters, we propose the microwave photonics approach with photo-mixing technique and the laser current controlling. Experimental results show that the optical frequency is stabilized with the accuracy of 0.05GHz.
13. Yudai Tatsumoto, Ryoga Kimura, Hirokazu Onji, Kazutoshi Kato, Hiroyuki Ishii, Makoto Shimokozono, High-speed, High-Accuracy 400-GHz Wavelength Switching at Tunable Distributed Amplification (TDA-) DFB Laser using Feedforward Control, 20th Optoelectronics and Communications Conference, 2015.07, [URL], We present the method of the high-speed wavelength switching of the tunable distributed amplification (TDA-) DFB laser by feedforward control. We designed and simulated the feedforward controller to accelerate the wavelength switching. A switching time of less than 100 ns with a frequency deviation of less than 1 GHz was achieved at switching toward 400-GHz spaced channels. The results indicate the feasibility of the TDA-DFB laser for future wavelength routing systems..
14. Kazuki Sakuma, Shota Takeuchi, Yuki Fujimura, Jun Haruki, Kazutoshi Kato, Shintaro Hisatake, Tadao Nagatsuma, First Demonstraion of Mach-Zehnder-Interferometric Phase-Stabilizaion at Optoelectronic Carrier Generation for Phase-Shift Keying Signal, 20th Optoelectronics and Communications Conference, 2015.06, [URL], We devised a phase stabilization technique at optoelectronic carrier generation applicable for the future THz wireless transmission. In this presentation we demonstrate at the first time that our technique using a Mach-Zehnder interferometric configuration is effective for the optoelectronic carrier for phase-shift keying signals as well as that for on-off keying signals by using an 1-Gbit/s binary-phase-shift keying transmission on a 12.5-GHz optoelectronic carrier..
15. Atsushi Saeki, Kazutoshi Kato, Fine wavelength stabilization of the DFB laser by photo-mixing with reference wavelengths, The Third International Japan-Egypt Conference on Electronics, Communications and Computers, March 17, 2015, 2015.03, The lasers for the future WDM system such as the flexible grid need to have highly accurate wavelength tuning which corresponds to the optical frequency stability within ±0.1 GHz. Instead of the use of the conventional wavelength locker which detects the optical frequency with optical filters, we propose the microwave photonics approach in which the beat signals are generated by photo-mixing with reference lights and filtered by the microwave filter. In this method the frequency accuracy depends on the accuracy of the microwave filter. Experimental results show that the optical frequency is stabilized at the grid with the accuracy of ±0.1 GHz by using the microwave filter..
16. Kazuki Sakuma, Shota Takeuchi, Yuki Fujimura, Jun Haruki, Kazutoshi Kato, Shintaro Hisatake, Tadao Nagatsuma, Mach-Zehnder Interferometric Phase Stabilization for Optoelectronic Carrier Generation, The Third International Japan-Egypt Conference on Electronics, Communications and Computers, March 17, 2015, 2015.03, We present a phase stabilization system of optoelectronic carrier generation for the future THz wireless transmission. The system has a Mach-Zehnder interferometric configuration and we transmitted 1-Gbit/s data at a 12.5-GHz carrier to confirm the effectiveness of the concept. We found that the noise floor which had been observed at the BER characteristics in our previous work disappeared with an optimized control and attained an error free performance..
17. Atsushi Saeki, Kazutoshi Kato, Fine wavelength stabilization of the DFB laser at the flexible grid by photo-mixing with reference wavelengths, 2014 Asia-Pacific Microwave Conference (APMC) 2014, FG1G-43, Sendai, 2014, 2014.11, The lasers for the flexible grid need to have highly accurate wavelength tuning which corresponds to the optical frequency stability within ±0.1 GHz. Instead of the use of the conventional wavelength locker which detects the optical frequency with optical filters, we propose the microwave photonics approach in which the beat signals are generated by photo-mixing with reference lights and filtered by the microwave filter. In this method the frequency accuracy depends on the accuracy of the microwave filter. Experimental results show that the optical frequency is stabilized at the grid with the accuracy of ±0.1 GHz by using the band elimination filter which has the 3-dB bandwidth of 0.1 GHz..
18. Shota Takeuchi, Kazutoshi Kato, Y.Yoshimizu, Y. Yasuda, Shintaro Hisatake, Tadao Nagatsuma, Coherent Sub-THz Carrier Frequency Transmission with Novel Pseudo-Mach-Zehnder Interferometric Phase Stabilization, 2014 International Topical Meeting on Microwave Photonics (MWP) 2014, TuEF-1, Sapporo, 2014, 2014.10.
19. Hirokazu Onji, Yudai Tatsumoto, Kazutoshi Kato, Nobuhiro Nunoya, Makoto Shimokozono, Hiroyuki Ishii, Stable Wavelength Switching within 50 ns using Tunable Distributed Amplification (TDA-) DFB Lasers
, 2014.08, Aiming fast wavelength switching for the tunable distributed amplification (TDA-) DFB lasers, the transfer function is deduced from the transient response and then the feedforward controller is designed. Experimental results show that the wavelength can be accurately stabilized within 35 ns and 30 ns when the optical frequency changes from 192.8 THz to 193 THz and vice versa, respectively..
20. Hirolazu Onji, Shota Takeuchi, Yudai Tatsumoto, Nobuhiro Nunoya, Makoto Shimokozono, Hiroyuki Ishii, Kazutoshi Kato, 35 ns Wavelength Switching with +/- 1 GHz Wavelength Accuracy using Tunable Distributed Amplification(TDA-) DFB Lasers, Photonics in Switching, Advanced Photonics for Communications, WPW4B.3, San Diego, USA, 2014 , 2014.07, For fast wavelength switching of TDA-DFB lasers, the feedforward controller is designed. Experimental results show switching times of 35 ns and 30 ns when the optical frequency changes from 192.8 THz to 193.0 THz and vice versa.
21. Shota Takeuchi, Kazutoshi Kato, Shintaro Hisatake, Tadao Nagatsuma, Sub-THz Carrier Frequency Generation Stabilized by Mach-Zehnder Interferometric Phase Detection Scheme, 19th Microoptics Conference, 2014.06, We propose a Mach-Zehnder interferometric phase detection for low phase noise subterahertz(THz) carrier frequency generation. In this scheme, phase fluctuation between two optical signals can be detected as the interference between their optical sidebands. Experimental result shows that, by controlling the interference to be constant, the phase noise is successfully reduced, which indicates effectiveness of the proposed method..
22. Optimization of Feedback Control Parameters for Tunable Lasers.
23. Shota Takeuchi, Hirokazu Onji, Nobuhiro Nunoya, Makoto Shimokozono, Hiroyuki Ishii, Kazutoshi Kato, WAVELENGTH STABILIZATION OF TUNABLE LASERS BASED ON THERMAL-DRIFT CANCELER, 18th Microoptics Conference (MOC'13), 2013.10, The wavelength stabilization based on the digitally controlled thermal-drift canceler is proposed and experimentally demonstrated. The tunable distributed amplification (TDA-) DFB laser controlled by this canceler reaches the targeted wavelength within a microsecond and keeps it stably..
24. Hirokazu Onji, Shota Takeuchi, Nobuhiro Nunoya, Makoto Shimokozono, Hiroyuki Ishii, Kazutoshi Kato, ACCELERATION OF WAVELENGTH SWITCHING FOR TUNABLE DISTRIBUTED AMPLIFICATION (TDA-) DFB LASERS
, 18th Microoptics Conference (MOC'13), 2013.10, The feedforward controller is designed and demonstrated to accelerate the wavelength switching for the tunable distributed (TDA) DFB lasers. The controller has an impulse overshoot waveform so as to induce prompt transition of short time phenomena. The controlled laser shows a wavelength switching time of 150 ns which shows effectiveness of the proposed technique..
Membership in Academic Society
  • The Laser Society of Japan
  • The Institute of Electrical and Electronics Engineers
  • The Japan Society of Applied Physics
  • The Institute of Electronics, Information and Communication Engineers
Educational
Educational Activities
Lecturer of "Material Science I" for 2rd-degree bachular students, "Electromagnetic wave enginering I" for 3rd-degree bachular students, "Elementary of Electromagnetism" for G30 students and "High-frequency devices" for 1st-degree master students, Superviser of three 4th-degree bachular students' graduation theses and eight master course students' theses.
Other Educational Activities
  • 2017.06.