| Project/Area Number |
03402031
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| Research Category |
Grant-in-Aid for General Scientific Research (A)
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| Allocation Type | Single-year Grants |
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| Research Field |
電子材料工学
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| Research Institution | University of Tokyo |
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Principal Investigator |
TADA Kunio Univ. of Tokyo, Faculty of Engineering, Professor, 工学部, 教授 (00010710)
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| Co-Investigator(Kenkyū-buntansha) |
MURAI Tohru Univ. of Tokyo, Faculty of Engineering, Assistant, 工学部, 助手 (60107571)
SHIMOGAMI Yukihiro Univ. of Tokyo, Faculty of Engineering, Lecturer, 工学部, 講師 (60192613)
NAKANO Yoshiaki Univ. of Tokyo, Faculty of Engineering, Associate professor, 工学部, 助教授 (50183885)
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| Project Period (FY) |
1991 – 1993
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| Keywords | Coupled quantum well / Parabolic potential quantum well / Quantum well with mass dependent width / Tensile-strained quantum well / Quantum confined Stark effect / Polarization independent optical modulation / Directional cou ; ler optical switch / Bistable optical device |
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| Research Abstract |
1.Electro-optic properties of coupled quantum wells : We have studied electro-adsorption in a system comprising a pair of quantum wells coupled through a thin barrierin between. Unique polarization dependence in such a system which seems useful for optical modulation has been found theoretically and experimentally. SEED bistable optical devices based on the coupled quantum wells have been fabricated. As a result, we have achieved a wide operation wavelength range (-15nm) and a low bias voltage(2V)
2.Polarization insensitive optical modulation using parabolic quantum wells : One of the problems in optical modulation with quantum wells is effective mass dependence of the quantum confined Stark effect (QCSE). We have solved the problem by making the potential profile of the quantum well into an effective paradolic profile. Polarization insensitive optical modulation by QCSE has been realized for the first time by introducing the parabolic quantum well to waveguide optical modulators
3.Polar
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ization insensitive optical modulation using quantum wells with mass-dependent width : We have proposed a novel quantum well structure with polarization insensitivity which is easy to grow and has larger tabrication tolerance. It consists of a square quantum well with two or four thin barriers inserted, and thereby its effective well width becomes dependent on effective mass. After theoretical analysis and design, we have fabricated a waveguide modulator with excellent characteristics, such as polarization-independent operation wavelength range as wide as 10nm and maximum extinction ratio as large as -28dB at 5V switching voltage
4.Growth of tensile strained quantum wells on GaAs substrates and its application : We have developed a technique to grow InAlAs substrates (having a larger lattice constant than GaAs) on GaAs substrates. By using this technique, tensile strained quantum wells are realized on GaAS substrates for the first time. They have been applied to a polarization insensitive optical modulator. Next, introduction of potential controlled structure to the tensile strained quantum wells has been investigated. As a result of theoretical analysis, we have predicted complete polarization insensitivity with TE/TM matching not only in exciton adsorption peak wavelengths but also in Stark shifts.
5.Directional coupler optical switch utilizing quantum wells : A novel coupling-coefficient modulation scheme in a transverse structure is proposed and fabricated. Consequently, we have achieved a 5V switching voltage in a 138um-long device. Product of the length and the switching voltage is the smallest ever reported Less
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