EFFECT OF ILLUMINATION UNIFORMITY ON GAAS PHOTOCONDUCTIVE SWITCHES

The dynamic behavior of a GaAs photoconductive switch was studied with an electro-optic imaging system during the first 2 ns after optical i llumination. The switch behavior changed as a function of the spatial distribution of the optical illumination. Symmetric and asymmetric ill umination schemes were investigated experimentally with our electro-op tic imaging system. The electric fields were significantly enhanced in the regions of low photo-carrier density, Approximately 1 ns after il lumination the simple longitudinal variation of the electric field gav e way to nonuniform transverse structure, The experimental results wer e modeled by treating the switch as an integral part of a transmission line consisting of discrete elements. The experimental results matche d the predictions of the transmission-line model in terms of the elect ric-field enhancements and efficiency.