1997 Fiscal Year Final Research Report Summary
Study of all-optical logic devices
| Project/Area Number |
07555339
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| Research Category |
Grant-in-Aid for Scientific Research (A)
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| Allocation Type | Single-year Grants |
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| Section | 展開研究 |
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| Research Field |
Applied optics/Quantum optical engineering
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| Research Institution | Tokyo Institute of Technology |
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Principal Investigator |
MIZUMOTO Tetsuya Tokyo Institute of Technology, Faculty of Engineering, Associate Professor, 工学部, 助教授 (00174045)
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| Co-Investigator(Kenkyū-buntansha) |
YOKOI Hideki Tokyo Institute of Technology, Faculty of Engineering, Research Associate, 工学部, 助手 (90251636)
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| Project Period (FY) |
1995 – 1997
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| Keywords | optical bistable device / optical logic / all-optical signal processing / optical nonlinear effect / intensity-dependent refractive index change / direct bandgap semiconductor / bandgap wavelength / distributed reflector |
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| Research Abstract |
The research was carried out in order to realize the waveguide optical switching devices controlled with light whose power is obtainable by a laser diode. The results obtained throughout this research are summarized as concluding remarks in the following.
The intensity-dependent refractive index and the nonlinear absorption coefficient were theoretically estimated in direct bandgap semiconductors. Through the numerical calculation, the required power to control a waveguide DFB bistable device composed of GaInAsP was estimated to be a few tens mW at a wavelength of 1550nm.
In case of conventional DFB structures with a uniform coupling coefficient, the on-state transmittance decreases as input intensity increases. This drawback, however, was overcome by introducing a weighted coupling coefficient in DFB structure. Through numerical calculations, it has been shown that optical bistable device with the weighted DFB structure exhibits improved on-state transmittance together with reduced threshold intensity. Also, nonlinear directional couplers loaded with a Bragg reflector (BR-NLDC), which work as a bistable device having two output ports separated from the input one, were proposed for optical signal processing applications. The swiching power of an asymmetric BR=NLDC is typically 1/10 less compared with a conventional nonlinear directional coupler.
Finally, all-optical switching was successfully demonstrated in the GaInAsP waveguide with a distributed feedback structure. The first observation of all-optical set-reset operation has been obtained in the waveguide structure compatible with optical integrated circuits. Through the present experiment, the threshold power for the optical swiching operation ranges from 20 to 80 mW.Although it is experimentally confirmed that the response time of devices is less than 2.5nsec, the limitation of the switching speed was not investigated. This must be done for practical applications in the future.
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