Smart pixels using the light amplifying optical switch (LAOS)

A light amplifying optical switch (LAOS), a vertically integrated heterojunction phototransistor (HPT) and light emitting diode (LED) that has latching thyristor type current-voltage characteristics, is described. Since the HPT is designed to have high optical gain, it can be incorporated in a circuit with the LAOS to fabricate high-performance optical logic gates such as a NOR, NAND, AND, or a gated latch. The methods for implementing these gates, experimental results for large mesa devices, and the performance of the gates are discussed. Logic gates that use either one or two wavelengths of input light are demonstrated. The present logic gates are shown to have output contrast ratios from 4 to 30, and operate at frequencies up to 300 kHz. Increasing this performance by improving processing techniques and reducing mesa size is discussed.>