Nonlinear Optics and Optical Switching in GaLAs and GaAs Near Half Band Gap

在过去的十年中，半导体，特别是GaAs和A1GaAs的非线性光学特性在其带隙附近得到了广泛的研究。并且在全光开关方面的应用有限。然而，人们对半导体的物理和应用所知甚少，其差距接近一半。我们在非线性定向耦合器上的初步结果表明，经典全光波导在带隙的一半以下具有切换的潜力。基于这一初步结果，我们提出研究GaAs和A1GaAs块体和MQW样品在其带隙一半附近的三阶非线性性质，即：1)测量非线性n2和双光子吸收系数B2的光谱依赖性，寻找间隙态、激子等引起的增强；2)利用下半带隙非线性来演示全光开关器件；3)研究空间孤子传播及其在A1GaAs逻辑器件中的潜在应用；4)研究二阶非线性的级联是否会导致大的三阶非线性。

In the last decade the nonlinear optical properties of semiconductors, especially GaAs and A1GaAs have been studied extensively near their bandgap, and have been applied with limited success to all-optical switching. However little is known about the physics and applications of semiconductors near half their gap. Our preliminary results on a nonlinear directional coupler have shown the potential for classical all-optical waveguide switching below half the band gap. Based on this preliminary result, it is proposed to investigate the third order nonlinear properties of bulk and MQW samples of GaAs and A1GaAs near half their band gap, that is to: 1) measure the spectral dependence of both the nonlinearity n2 and two photon absorption coefficient B2, looking for enhancements due to gap states, excitons ets; 2) use the below half band gap nonlinearities to demonstrate all-optical switching devices; 3) investigate spatial soliton propagation, and its potential application to logic devices in A1GaAs; 4) study whether the cascading of second order nonlinearities can lead to large third order nonlinearities.