Light-Induced Critical Behavior in the Four-Wave Interaction in Nonlinear Systems

It is shown that the four-wave interaction of a powerful stationary pump field and a weak signal field in a dielectric modeled with an assembly of anharmonically interacting particles exhibits a behavior radically different from that expected from the usual perturbation theory assuming small oscillation amplitudes. A light-induced critical behavior in the intensity of the reflected phase-conjugated field is obtained as a consequence of the interaction of the pump with the matter.