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

We report a surface-normal optically controlled optoelectronic modulator made from a reversed biased p-i ~multiple quantum well!-n GaAs/AlGaAs structure with ultrathin barriers ~5 Å! whose recovery time is based on diffusive conduction. Modulation of reflectivity from 0.3 to 0.6 and back again in about 50 ps was demonstrated using a 750 fJ control pulse at 855 nm. We also demonstrated modulated changes in power greater than the control pulse power—a type of signal gain—by a factor of 1.8-to-1. Strong changes in reflectivity combined with low required control power make this device potentially useful for high-speed switching arrays in such applications as time division demultiplexing. © 1999 American Institute of Physics. @S0003-6951~99!00331-9#