Modified SCR for optically actuated triggering

A simple inexpensive, optically actuated triggering device (optical trigger) has been developed for synchronizing pulsed lasers with signal gathering instrumentation. The heart of this device is a commercially available SCR that has been modified for light activated operation. The optical trigger delivers, into a 50-Omega load, a pulse of either 84 V with a 8.3-ns rise time and 3.5-micros width, or 42 V with a 6.2-ns rise time and 7-micros width. The device is sensitive throughout the visible and near-visible spectrum. It has a transit time of only 2.2 ns and less than 1-ns jitter. The performance of this optical trigger is examined in terms of the criteria of an ''ideal'' optical trigger and the effects of circuit and input parameters on output pulse characteristics are discussed.