The effect of carrier sweepout on performance of semi-insulating multiple quantum well photorefractive devices

Abstract

We have studied the effect of barrier design on the grating period dependence of the diffraction efficiency in semi-insulating GaAs/AlGaAs and CdZnTe/ZnTe multiple quantum well photorefractive devices in the geometry with the applied field perpendicular to the quantum wells. In GaAs/ AlGaAs devices, lowering of the barrier height by reduction of Al concentration from 40% to 30% and reduction of barrier thickness from 100 Å to 35 Å increases the diffraction efficiency by 5 orders of magnitude. This is due to the reduction in carrier sweepout time from the quantum wells reducing the lateral diffusion of carriers in the wells. In an optimized structure, a diffraction efficiency of 3% at 852 nm from a 2 pm thick sample is obtained by application of 20 V. We will discuss the relevant parameters in the design of a photorefractive multiple quantum well device. As an application, the performance of a joint transform correlator based on a multiple quantum well photorefractive device and diode lasers will be discussed.