Research on Optical Modulators and Switches Based on Potential-Tailored Quantum Microstructures for the Advanced Optical Communication Infrastructure

点击翻译按钮获取中文摘要

1. Proposal and Design of the Five-Step Asymmetric Coupled Quantum Well (FACQW) :A potential-tailored quantum well structure named as above was proposed and designed. This FACQW, in contrast to the conventional rectangular quantum well (RQW), can produce very large field-induced refractive index change DELTAn in the transparency wavelength region far from the absorption edge. An example of calculated results for the A1GaAs material system is that An under applied field of 10 kV/cm is as large as 0.002 at 830 nm wavelength which is apart from the absorption edge by 40 nm.2. Implementation of Ultra-Fast and Low-Voltage Optical Modulator :As an application of the FACQW, a traveling-wave type Mach-Zehnder interferometer modulator with 2 mm-long arms of optical waveguide composed of 20 sets of the FACQW was fabricated. At 850 nm wavelength, the modulation bandwidth and the switching voltage were measured as 55 GHz and 3 V, respectively. To our knowledge, this is the first traveling-wave type multiple quantum well (MQW) waveguide modulator, and the above modulation bandwidth exceeds the highest value ever reported on semiconductor optical modulators.3. Analysis and Improvement of the FACQW :The above experimental result indicates that DELTAn in the FACQW is a few times as large as DELTAn in the RQW, but is smaller than the calculated value by about one order of magnitude. To clarify the reason for his discrepancy, some simulation analyses have been carried out concerning influences of the layer thickness fluctuation. Some modified structures of the FACQW have also been obtained with higher An or better linearity of DELTAn.4. Other Potential -Tailored Quantum Well Structures :Two new structures have been proposed and studied for electroabsorptive modulators for