Subnanosecond, high-voltage photoconductive switching in GaAs

In this paper, the authors conduct research on the switching properties of photoconductive materials to explore their potential for generating high-power microwaves (HPM) and for high rep-rate switching. The authors have investigated the performance of Gallium Arsenide (GaAs) in linear mode (the conductivity of the device follows the optical pulse) as well as an avalanche-like mode (the optical pulse only controls switch closing). Operating in the linear mode, the authors have observed switch closing times of less than 200 ps with a 100 ps duration laser pulse and opening times of less than 400 ps at several kV/cm fields using neutron irradiated GaAs. In avalanche and lock-on modes, high fields are switched with lower laser pulse energies, resulting in higher efficiencies; but with measurable switching delay and jitter. The authors are currently investigating both large area (1 cm2) and small area (<1 mm2) switches illuminated by AlGaAs laser diodes at 900 nm and Nd:YAG lasers at 1.06 μm