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

1.耦合量子威尔斯阱的电光特性：我们研究了一对通过薄势垒耦合的量子威尔斯阱系统中的电吸附。在理论和实验上发现了这种系统中独特的偏振依赖性，这似乎对光学调制有用。制备了基于耦合量子威尔斯阱的籽晶外延光学器件。2.抛物型量子威尔斯光调制的偏振不敏感性：量子威尔斯光调制中的一个问题是量子限制斯塔克效应（QCSE）的有效质量依赖性。我们通过将量子阱的势分布变为有效的抛物线分布，解决了这个问题。通过在波导光调制器中引入抛物量子阱，首次实现了偏振不敏感的QCSE光调制 关于我们 利用具有质量依赖宽度的量子威尔斯实现偏振不敏感的光调制：我们提出了一种具有偏振不敏感的新型量子阱结构，该结构易于生长并且具有较大的偏振容限。它由插入两个或四个薄势垒的方形量子阱组成，因此其有效阱宽度取决于有效质量。经过理论分析和设计，我们研制出了一种性能优良的波导调制器，其偏振无关工作波长范围宽达10 nm，在5V开关电压下最大消光比达-28dB。4. GaAs衬底上张应变量子威尔斯阱的生长及其应用：我们已经开发了一种技术，以生长InAlAs衬底（具有较大的晶格常数比GaAs）上GaAs衬底。利用该技术，首次在GaAs衬底上实现了张应变量子威尔斯阱。它们已应用于偏振不敏感光调制器。接下来，研究了将势控结构引入拉伸应变量子阱威尔斯。作为理论分析的结果，我们预测了TE/TM匹配不仅在激子吸收峰波长上而且在斯塔克位移上都是完全偏振不灵敏的。5.利用量子威尔斯的定向耦合器光开关：提出并制备了一种新颖的横向结构的耦合系数调制方案。因此，我们已经实现了5V的开关电压在138微米长的设备。长度和开关电压的乘积是有史以来报道的最小的

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