Linear- and nonlinear-optical properties of free and bound excitons in CdS and applications in bistable devices

A general discussion of the linear-optical properties of free and bound excitons in direct-gap semiconductors at low temperature is presented. This discussion then specializes to CdS. The nonlinear-optical response of CdS is introduced by first discussing the saturation behavior of bound excitons. A new type of cavityless optical bistability based on induced absorption near the free and bound excitons is described. Finally, fast all-optical switching (<1 nsec) at very low switching energies (<8 pJ) is demonstrated, using the giant nonlinearity associated with bound excitons.