Electro-optical hysteresis and bistability in the ring-cavity tunneling-collector transistor laser

Bistable devices are fundamental to digital electronics as building blocks of switches, logic gates, and memory in computer systems. We demonstrate here transistor lasers exhibiting both electrical and optical hystereses with sharp square-corner current switching and different voltage thresholds in the collector I_C-V_CE and optical L-V_CE family of characteristics. The electro-optical hysteresis is explained by the different switching paths of electron-hole (e-h) and photon interactions involving cavity coherent and incoherent energy states employing intracavity photon-assisted tunneling at the collector junction and spontaneous/stimulated e-h recombination at the base quantum-well. The electro-optical bistability of the transistor laser possesses a unique property of voltage (field) modulation and the basis for high speed optical logic processors.