High-speed, optically controlled surface-normal optical switch based on diffusive conduction

We report a surface-normal optically controlled optoelectronic modulator ma de from a reversed biased p-i (multiple quantum well)-n GaAs/AlGaAs structu re with ultrathin barriers (5 Angstrom) whose recovery time is based on dif fusive conduction. Modulation of reflectivity from 0.3 to 0.6 and back agai n in about 50 ps was demonstrated using a 750 fJ control pulse at 855 nm. W e also demonstrated modulated changes in power greater than the control pul se power-a type of signal gain-by a factor of 1.8-to-1. Strong changes in r eflectivity combined with low required control power make this device poten tially useful for high-speed switching arrays in such applications as time division demultiplexing. (C) 1999 American Institute of Physics. [S0003-695 1(99)00331-9].