Optical bistability in a single semiconductor transistor laser are realized and demonstrated based on the modulation of cavity photon density via the base quantum-wells for photon-generation and collector intra-cavity photon assisted tunneling for photon-absorption.
Optical bistable devices are fundamental to digital photonics as building blocks of switches, logic gates, and memories in future computer systems. Here, we demonstrate both optical and electrical bistability and capability for switching in a single transistor operated at room temperature. The electro-optical hysteresis is explained by the interaction of electron-hole (e-h) generation and recombination dynamics with the cavity photon modulation in different switching paths. The switch-UP and switch-DOWN threshold voltages are determined by the rate difference of photon generation at the base quantum-well and the photon absorption via intra-cavity photon-assisted tunneling controlled by the collector voltage. Thus, the transistor laser electro-optical bistable switching is programmable with base current and collector voltage, and the basis for high speed optical logic processors.
Abstract Optical bistability (OB) is a phenomenon that describes a light induced phase transition in the non-equilibrium state. It is vital for all-optical computing and communication, serving as the basis for switches, logic gates, transistors, and memory. By enabling two stable light states, OB allows storage and fast switching, making high-speed, energy-efficient data processing possible. In this work we study the phenomenon in a two-band semiconductor in an optical cavity. Starting from a many-body Hamiltonian of optically generated electrons, holes and light-semiconductor interaction and Coulomb electron–electron, hole–hole and electron–hole interactions, we obtain the optical Bloch equations, in the mean field approximation, where relaxation is included phenomenologically. We obtain expressions for particle density, excitonic pair density and output intensity as non-linear functions of input light intensity. All these quantities show bistable behaviour, with two stable phases, and hysteresis in the non-equilibrium state. Equilibrium is ensured by introducing damping terms for the particle density amplitude, excitonic density amplitude, and cavity photon amplitude phenomenologically. The electron–hole pairs increase with light intensity, shows bistable features and then disappears with further increase in the input light intensity. The bistable behaviour becomes pronounced as we pass from low Coulomb interaction strengths to high Coulomb interaction strengths between electrons and holes. For sub-bandgap excitations, the output light versus incident light shows a complex behaviour.
We theoretically investigate the optical bistability in a composite photonic molecule cavity optomechanical system consisting of two whispering gallery mode microcavities, where one of the optical cavities is optomechanical with a high quality factor, and the other optical cavity is an auxiliary cavity with high cavity dissipation. By controlling the coupling strength J between the two cavities determined by their distance, the decay rate ratio δ of the two cavities, and the pump power P, the optical bistability can be controlled. Further, the transmission spectrum of the signal field can be efficiently attenuated or amplified, depending on the power of a second “gating” (pump) field P, and other parameters. Our study for photonic-molecule optomechanics systems may be a promising candidate for single-photon transistors and pave the way for potential applications in quantum information technologies.