| Co-Investigator(Kenkyū-buntansha) |
KATO Masaki The University of Tokyo, Graduate School of Frontier Science, Research Associate, 大学院・新領域創成科学研究科, 助手 (80312982)
SHIMOGAKI Yukihiro The University of Tokyo, Graduate School of Engineering, Associate Professor, 大学院・工学系研究科, 助教授 (60192613)
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| Research Abstract |
1.Fabrication of Chirped gratings by weighted electron beam exposure and their application to DFB lasers : By combining a field size modulation technique with the weighted electron beam exposure, we successfully fabricated linearly chirped gratings (CGs). Then, we applied them to distributed feedback (DFB) laser fabrication, and observed optical bistability in the CD DFB lasers. The optical power necessary to excite the bistability was found to be one fourth of conventional DFB lasers, and the wavelength range within which the bistability was observed was twice as large as the conventional ones.
2.Mass-transported InAsP compressively-strained quantum wire gain-coupled DFB laser fabrication : Mass-transport phenomenon on InGaAsP/InP epitaxial wafers with quarter micron pitch V-grooves was made use of for the fabrication of quantum wire gain-coupled DFB lasers. Amplified spontaneous emission (ASE) around 1.55 μm was observed.
3.Wavelength trimming in multiple wavelength gain-coupled DFB la
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yer arrays : Multiple wavelength gain-coupled DFB laser arrays were studied and fabricated as a light source for wavelength division multiplexed (WDM) optical communication. The multiple pitch gratings were formed by electron beam exposure with field size modulation, and the gain coupling was brought about by absorptive gratings. The four wavelength laser array at 1.55μm band fabricated exhibited uniform threshold current distribution and oscillation wavelength spacing. Disordering experiment of a super lattice layer by a pulsed YAG laser beam was conducted for wavelength trimming.
4.Temperature insensitive semiconductor laser by strain compensation : Toward "fiber to the home" and its wavelength multiplexing, we studied reduction of temperature sensitivity in laser diode characteristics. More specifically, we tried to cancel out intrinsic temperature dependence by applying mechanical strain to laser diodes with temperature change through novel heat-sink structure. After remodeling of the heat sink, we packaged laser chips on it and demonstrated feasibility of temperature compensation of oscillation wavelength and threshold current by this method.
5.All optical_flip-flop based on bistable semiconductor lasers : We proposed a novel bistable directionally coupled semiconductor laser as an all-optical flip-flop important for future all-optical processing. After confirming its effectiveness through theoretical analysis, an actual device was fabricated by utilizing newly developed electrode separation technique. As a result, all-optical flip-flop operation was demonstrated. Less
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