Multiple spontaneously generated coherence and phase control of optical bistability and multistability in a tripod four-level atomic medium.

Optical bistability (OB) and optical multistability (OM) behaviors induced by multiple spontaneously generated coherence (SGC) are investigated theoretically in a tripod four-level atomic scheme. It is found that OB or OM is sensitive to the SGC effects, and the thresholds of OB can be controlled via changing the strength of multiple SGC or the relative phases of the applied fields. In addition, we can switch OB to OM by adjusting the twofold relative phases of the applied fields or vice versa.