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.