Integrated All-Optical Devices Fabricated Using Area-Selective Disordering of Multiple Quantum Well Structures

Abstract

ABSTRACTWe describe a method of silicon oxide capped disordering of GaAs /AlGaAs multiple quantum wells (MQW) and its application to the fabrication of passive waveguides integrated with nonlinear switching sections. The silicon oxide cap in this work was formed by spinning a solution of glass forming compound and curing it. The characteristics of the disordering process has been studied by monitoring the shift of the photoluminescence as a function of rapid thermal annealing temperature and fitting the n=1 electron heavy-hole level to that calculated from an error function diffusion profile. Our results indicate a Ga-Al inter-diffusion constant of 8×10−16 cm2s−1 at 980°C and an activation energy of 4.4eV which is similar to values reported by other researchers.The disordering process is then used to define selected areas of disordered and non-disordered MQWs and ridge waveguide structures were fabricated by conventional photolithography and wet chemical etching. Two structures have been studied. One is the nonlinear zero-gap directional coupler with disordered input and output branching waveguides, and the other is the symmetric nonlinear integrated Mach-Zehnder interferometer with one arm containing a non-intermixed MQW section. The devices investigated using a pump-probe set-up, exhibited strong all-optical switching behavior with a contrast ratio of 15:1.