Optical properties of modified potential quantum micro structures and their application to optical modulationlswiching devices

1.短波长（0.8 μ m）完全偏振无关光调制器的研制我们在GaAs衬底上通过在GaAs/InGaAs应变超晶格缓冲层之间放置GaAs/InGaAs应变超晶格缓冲层，制备了晶格常数比GaAs大的InGaAs赝衬底。在其顶部，我们成功地生长了GaAs量子阱威尔斯，量子阱的宽度与量子阱的宽度有关。将该晶片制成光强度调制器，并对其光调制特性进行了表征。因此，我们实现了在28 nm波长范围内0.8 μ m附近消光比大于10 dB的完全偏振无关光调制。2.长波长外延生长技术（1.55 μ m）完全偏振无关的光调制器我们研究了InP衬底上InGaAs/InAlAs应变量子威尔斯的分子束外延，针对基于与上述相同原理的完全偏振无关的光调制器， ...更多信息 光通信波段。通过优化生长温度、选择铟源材料和InP衬底，使高质量应变量子威尔斯阱的外延生长成为可能。其次，我们生长了双异质结，并将其制成脊形波导结构，利用法布里-珀罗干涉测量了其传输损耗。3.低插入损耗的表面垂直光开关我们利用耦合量子阱结构中带边的有效蓝移，降低了表面垂直光开关器件（SEEDs）在导通状态下的剩余插入损耗。我们还从实验和理论上证明，通过使用非对称三重耦合量子威尔斯阱，不仅可以改善剩余损耗，而且可以改善ON和OFF状态之间的对比度。另一方面，通过特殊的对称耦合量子威尔斯阱结构，可以利用低电场区的大吸收变化。利用改进的势不对称耦合量子威尔斯阱结构制备了透射型对称单量子阱器件，并在其中实现了光调制。4.行波量子阱高速光调制器制作了共面行波电极GaAs定向耦合器光调制器，并用扫频法表征了其光调制性能。5.修正势五阶非对称耦合量子阱我们发现了一种特殊的量子阱结构，它在低电场下可以获得大的折射率变化，而不会激发吸收边的红移。少

SUMMARY OF RESEARCH RESULTS1.Development of short wavelength (0.8mum)completely-polarization-independent optical modulatorWe made an InGaAs pseudo substraste with larger lattice constant than GaAs on a GaAs substrate by sandwiching GaAs/InGaAs strained super lattice buffer layr between them. On its top, we grew GaAs tensilestained quantum wells with mess-dependent width successfully. The wafer was made into optical intensity modulators and their optical modulation properties were characterized. Consequently, we have achieved complete polarization-independent optical modulation with extinction ratio larger than 10 dB over the wavelength range of 28 nm around 0.8mum band.2.Epitaxial growth technique toward long wavelength (1.55mum) completely-polarization-independent optical modulatorWe studied molecular beam epitaxy of lnGaAs/lnAlAs strained quantum wells on lnP substrates, aiming at completely-polarization-independent optical modulators based on the same principle as above in 1.55mum o … More ptical communication wavelength band. By optimizing growth temperature and by carefully selecting indium source materials and InP substrates, epitaxial growth of strained quantum wells with excellent quality was made possible. Next, we grew double heterostructure, made it into ridge waveguide configuration, and measured its propagation Ioss by using the Fabry-Perot interference.3.Surface vertical optical switches with low insertion lossWe reduced remaining insertion loss at ON atate in surface-vertical optical bistable devices, namely, SEEDs, by utillzing effective blue shift of band edges in coupled quantum well structures. we also showed, We also showed, experimentally and theoretically, that not only the remaining loss but also the contrast between ON and OFF atate could be improved throved through the use of asymmetric triple coupled quantum wells. On the other hand, utilization of large absorption change in low electric field region was made possible by a special symetric coupled quantum wells. We fabricated transmission-type symmetric SEEDs by making use of a modified potential asymmetric coupled quantum wells and accomplished optical bistable operation in them.4.Traveling wave quantum well high speed optical modulatorWe fabricated a GaAs directional coupler optical modulator with coplanar traveling-wave electrodes, and characterterized its optical modulation performance using the swept-frequency method. Bandwidth of 22 GHz was achieved.5.Modified-potential five-step asymmetric coupled quantum wellsWe found a special quantum well structure where a large index change is obtainable at low electric field without exciting red-shift of absorption edges. Less