Optical Bistability: Steady-State and Transient Behavior

Abstract

An optical system that can exist in either of two distinct stable transmission states for a given input intensity is said to exhibit optical bistability. For this to occur, the system's transmission properties must depend on its output; that is, feedback is necessary. This feedback can be provided by placing a nonlinear material inside an optical resonator. Two mechanisms can then give rise to bistability, and the bistability is classed as absorptive or dispersive according to the nature of the responsible nonlinearity. In absorptive bistability, the input light is resonant with both the resonator and the absorbing medium. For low input intensities, the medium attenuation prevents appreciable feedback from taking place, and the system's transmission is low; at some higher input intensity, sufficient light gets through the medium to the output mirror and is reflected back to help saturate the absorption. This in turn means that more light gets through the medium, and the process continues in a runaway manner until the absorption is fully saturated. The result is complete constructive interference in the resonator and hence a large system transmission. The saturation persists as the input intensity is decreased, resulting in hysteresis in the transmission as shown in Fig. 1. Dispersive bistability occurs when the frequency of the input light is offset from resonance with the- medium and with the resonator; the intensity-dependent nonlinear dispersion can then bring the cavity into resonance, making the transmission high.

Additional details