Quantum interference in phase conjugation by resonant, nearly degenerate four-wave mixing

We present a theoretical investigation of optical phase conjugation by use of nearly degenerate four-wave mixing in a two-level atomic system. The des cription is based on the semiclassical dressed-state approach, which offers a very transparent picture of the physics involved in the nonlinear proces s. The theory provides an explanation in terms of a quantum interference be tween two channels for the strong reduction of the optical phase-conjugate yield when the pump fields are tuned to the atomic resonance. In addition, the model predicts an efficient generation of the optical phase conjugate i f the system is prepared in a pure dressed state. [S1050-2947(99)08708-9].