Optical bistability and multistability via atomic coherence in anN-type atomic medium

We analyze hybrid absorptive-dispersive optical bistability (OB) and multistability (OM) behavior in a generic $N$-type atomic system driven by a degenerate probe field and a coherent coupling field by means of a unidirectional ring cavity. We show that the OB can be controlled by adjusting the intensity and the detuning of the coupling field, and the OM can also be observed under the appropriate detuning. The influence of the atomic cooperation parameter on atomic OB behavior is also discussed.