Optical bistability and multistability induced by quantum coherence in diamond germanium-vacancy color centers.

Optical bistability (OB) and optical multistability (OM) behaviors are investigated theoretically in a four-level Ntype diamond germanium-vacancy (GeV) color center scheme immersed in a unidirectional ring cavity based on electromagnetically induced transparency (EIT). It is found that OB behavior is very sensitive to the system parameters, such as the detunings of probe and coupling fields and the intensities of coupling fields as well as the density of GeV centers, and the thresholds of OB can be controlled via changing these parameters. In addition, we can switch OB to OM by adjusting the intensity of control field and the density of GeV centers or vice versa. Our results may provide some guidance for an all-optical switching, optical communications, and optical logic devices in a solid-state system. (C) 2019 Optical Society of America