Tunable Optical Bistability of Bichromatic Fields Interacting with Four-Level Systems

A simple four-level model is used to describe two-band systems such as dyes and semiconductors. The system is irradiated by a bichromatic input in an optical cavity and both fields exhibit optical multistability. The calculations take into account the possibility of noncoherent (electrical) pumping of the system, thus generalizing the model to include semiconductor laser amplifiers. Since both fields are allowed to resonate in the cavity, a low-intensity control beam and/or the noncoherent pumping intensity can “tune” and adapt the response of the second input. Some applications of this tunability are outlined.