Cascadable laser logic devices: discrete integration of phototransistors with surface-emitting laser diodes

A new class of cascadable optical logic devices is described which consists of integrated GaAs/AlGaAs phototransistors and surface-emitting lasers. The devices function as optical neurons (‘smart pixels’), have high optical gain (a factor of >20 overall, >200 differential), very high on/off contrast (>2700, 34dB) and are ideal for neural networks and optical computing applications.