Semiconductor Bistable Etalons for Digital Optical Computing

Abstract

A large number of semiconductors have now been shown to exhibit optical bistability under appropriate conditions. Optical bistability, a process in which an element illuminated with a given optical power can exist in one of two possible stable transmission (or reflection) states, requires two conditions, (a) an optical nonlinearity and (b) some form of feedback. Bistable devices able to operate as short term memory elements and perform the fundamental logic operations have been demonstrated at low power levels. For semiconductors, large band gap resonant nonlinearities can be employed which reduce the optical input power requirements to milliwatts or less. The feedback may be produced by housing the nonlinear material within a Fabry-Perot etalon or using the intrinsic feedback associated with the dependence of optical absorption on a parameter such as temperature. Alternatively, the nonlinearity may be artificially created using electro-optic effects and electrical feedback.