Chaos in photorefractive four-wave mixing with a single grating and a single interaction region

Abstract

We show that the standard model of four-wave mixing in a photorefractive crystal predicts the appearance of deterministic chaos. In this model there is a single (transmission) grating and no external or internal (intracavity) feedback. The intensity of the phase-conjugate wave is found to exhibit a period-doubling route to chaos on variation of the intensity of the probe beam and the linear absorption coefficient. The crucial elements in obtaining chaotic behavior are operation above the threshold for self-oscillation and the presence of an external electric field, which causes a shift in the optical frequency of the phase-conjugate wave.