Abstract In this paper, recent advances in optical bistability and gating of semiconductors will be reviewed. Nonlinear mechanisms responsible for switching will be described. The advantages of nonlinear etalons for massive parallelism and current problems in performing such operations will be mentioned.
In this paper we present the basic principles of optical bistability and summarize the current advances in semiconductor optical switching, with emphasis on recent results in GaAs, CuCI, InAs, InSb, CdS, ZnS, and ZnSe etalons. These devices have great potential for applications involving optical signal processing and computing. As an example, we discuss the use of arrays of bistable devices for parallel optical processing and for addressable spatial light modulators. The use of nonlinear etalons as optical gates is also illustrated. To date, GaAs devices have shown the most favorable characteristics for practical applications. They operate at room temperature with a few milliwatts of power using a laser diode as the only light source. Quasi-cw operation and optical fiber signal regeneration have also been demonstrated. A GaAs NOR gate operates in 1 ps with <3 pJ incident energy; this, of course, implies a 1 ps switch-on time for a bistable etalon.
Optical bistability can be obtained in nonlinear materials either with Fabry-Perot mirrors or without external feedback. When a material is placed between partially reflecting mirrors, a nonlinear Fabry-Perot etalon is formed with the etalon providing an external feedback. Optical bistability and gating occur as a result of a shift in the Fabry-Perot peak when the light intensity is increased (or when a second laser beam is introduced into the cavity). Optical bistability with the external feedback mechanism has been observed in many semiconductors such as bulk GaAs, GaAs-AIGaAs multiple-quantum-well (MQW) structures, InSb, InAs, CdS, CdHgTe, GaSe, and CuCI.
This article describes the application of one type of optical bistable device based on gallium arsenide as the nonlinear medium. The authors discuss several possible operations with GaAs nonlinear Fabry-Perot etalons. This article utilizes a recently developed computer model to illustrate the basic operating principles and applications. The authors mainly concentrate on the device operation itself. In keeping with common practice they use the term optical bistable device when referring to a device that can exhibit optical bistability even when not being used in such a manner. Instead of the expression nonlinear Fabry-Perot etalon, they often use nonlinear etalons or etalon devices.
We present a review of optical bistability in active and passive optoelectronic devices, with particular reference to switching speeds and powers. The large resonant nonlinearities available near the bandgaps of semiconductors may be utilized to develop bistable devices operating at low powers and high speeds. Passive devices are driven by external optical sources and include nonlinear etalons, nonlinear interfaces, self-focusing configurations and electro-optic modulators with electrical feedback. Active devices include injection lasers and superluminescent amplifiers. Potential advantages of active devices include speed, gain, sensitivity and the ability to drive other devices, but complexity and high power dissipation may limit their use in applications requiring high density.