Bistable Optoelectronic Devices in GaAs

Bistable switching devices occupy a central role in the area of signal processing. Electronic switching devices (electrical in - electrical out) commonly known as Schmidt trigger are key elements in the general area of analog and digital signal processing by electronic means. It seems inevitable that optical computing and signal processing systems will eventually incorporate some form of optical bistable switching elements. Purely optical bistable devices (optical in - optical out) have, through investigations in recent years, made very substantial advances in terms of switching speed and optical power requirements. In order to extend the range of problems that optical computing systems are capable of handling, it has been suggested that future optical computing systems may not be purely optical in nature but rather an amalgam of optical and electronic processing elements in order to take advantage of the best of both worlds. In this respect, bistable optoelectronic devices that are capable of switching by optical and/or electrical signals, and have their outputs available in both optical and electrical forms, may play a unique and useful role in these hybrid systems. Recent advances in these kinds of bistable devices based on interaction of optical (lasers, detectors) and electronic (transistors) devices monolithic integrated on GaAs substrates will be described in this paper. Switching speeds in the sub-nanosecond regime (as short as 50ps) and optical switching powers in the 10mW/cm2 range have already been demonstrated in these devices. The purpose of this presentation is to familiarize researchers in the field of optical computing with new possibilities and venules of investigations brought about by these recent advances.