Intracavity resonant degenerate 4-wave mixing in atomic sodium vapor: Bistability in phase conjugation

We report on intracavity phase conjugation via resonant degenerate 4-wave mixing in atomic sodium vapor with the use of transverse optical Zeeman pumping as a versatile nonlinear mechanism. Under appropriate conditions the phase conjugate wave is found to display bistability, polarization switching and magnetically-induced selfoscillations. Our measurements are shown to be in fair agreement with theoretical predictions based on a simple analytic treatment for a homogeneously broadened coupled 4-level system.