Advanced photonic functional materials based on quantum microstructures with atomic scale precision and their application to optical modulation / switching

1.耦合量子阱的电光特性：我们研究了由一对量子阱组成的系统中的电吸附。在理论上和实验上都发现了这种系统中独特的偏振依赖关系，这对光调制似乎是有用的。制备了基于耦合量子阱的SEED双稳光学器件。因此，我们实现了宽工作波长范围（-15nm）和低偏置电压（2V）2。利用抛物型量子阱进行偏振不敏感光调制：利用量子阱进行光调制的问题之一是量子受限斯塔克效应的有效质量依赖。我们通过将量子阱的势轮廓变成有效的佯谬轮廓来解决这个问题。通过在波导光调制器中引入抛物量子阱，首次实现了QCSE的偏振不敏感光调制。利用具有质量相关宽度的量子阱进行极化不敏感光调制：我们提出了一种新的极化不敏感量子阱结构，该结构易于生长，并且具有较大的折叠容忍度。它由一个方形量子阱和两个或四个插入的薄势垒组成，因此它的有效阱宽度取决于有效质量。经过理论分析和设计，我们制作了一个具有优异特性的波导调制器，在5V开关电压下，其偏振无关工作波长范围可达10nm，最大消光比可达-28dB。GaAs衬底上拉伸应变量子阱的生长及其应用：我们开发了一种在GaAs衬底上生长InAlAs衬底（具有比GaAs更大的晶格常数）的技术。利用该技术，首次在GaAS衬底上实现了拉伸应变量子阱。并将其应用于偏振不敏感光调制器中。其次，研究了在拉伸应变量子阱中引入电位控制结构。通过理论分析，我们预测了TE/TM不仅在激子吸附峰波长上匹配，而且在斯塔克位移上也匹配的完全极化不敏感。利用量子阱的定向耦合器光开关：提出并制作了一种新的横向结构的耦合系数调制方案。因此，我们在138um长的器件中实现了5V的开关电压。长度与开关电压的乘积是迄今为止报道的最小的

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 modulators3.Polar … More 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 voltage4.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