Phase conjugation in critical microemulsions

We present a model to describe degenerate four-wave mixing in critical binary liquid mixtures and we analyze it through an experimental study of phase conjugation in critical microemulsions. The two concentration gratings related to the four-wave-mixing configuration give contributions to the conjugated signal which can be separated from their different formation and relaxation times. The model quantitatively describes the amplitude and the dynamics of the gratings and thus of the conjugate signal when one approaches the critical point. The theoretical predictions fit very well with the experimental data. Close to the critical point a 10% reflectivity has been obtained in this medium using a beam power of 1 W from a cw Ar⁺ laser. The limitations of these reflectivities at higher powers are discussed.