Dynamic all-optical memory switching based on atomic optical bistable behavior in a three level Λ-type atomic system

We theoretically investigate the atomic optical bistability (AOB) in a three-level Λ-type atomic system confined in a unidirectional optical ring cavity. The role of the intensity or detuning of the control field on AOB is explored, and results show that absorption, dispersion, and nonlinearity can be modified significantly by the control field due to quantum coherence and interference in multilevel atomic systems. Thus, tuning the intensity or detuning of the control field can manipulate the switch-up and switch-down thresholds, as well as the area of the bistable hysteresis loop. According to the controllability of AOB, we design various schemes to realize dynamical all-optical switching between the high and low outputs of two bistable curves for a fixed cavity input. In addition, dynamical all-optical memory switching can be implemented by adding a pulse sequence for the intensity or detuning of the control field. For appropriate parameters, such as the cooperative coefficient, the extinction ratio of the switching can be improved dramatically.