<title>High-gain GaAs photoconductive semiconductor switches (PCSS): device lifetime, high-current testing, optical pulse generators</title>

Abstract

This paper presents results from three areas of GaAs PCSS research and development: device lifetime, high current switching, and PCSS-driven laser diode arrays (LDA). We have performed device lifetime tests on both lateral and vertical switches as a function of current amplitude, pulse width, and charging time. At present, our longest-lived switch reached 4 X 10<SUP>6</SUP> pulses. Scanning electron microscope (SEM) images show damage near the contacts even after only 5 pulses. We are presently searching for the threshold at which no damage is evident after a single shot. In high current tests, we have reached 5.2 kA at 4.2 kV. This was achieved using twenty fiber-optic coupled lasers to distribute current filaments over a 5 mm wide PCSS. Current waveforms and images of the current filaments as a function of current amplitude will be presented. The lasers used to trigger the high current PCSS were driven with a miniature PCSS. Low inductance, high speed GaAs PCSS are very effective as short pulse laser diode array drivers. Some types of arrays gain switch, producing a compressed optical pulse which is only 57 ps wide. Results from tests with a variety of laser diode arrays will be presented.