Two-dimensional degenerate mixing of two waves in a nonlinear medium

An analysis is made of the interaction of two coherent waves of different intensities in a thin layer of a transparent nonlinear medium. It is shown that such interaction or mixing can amplify the weaker wave without altering its wave front. A report is given of an experimental demonstration on the amplification of a spherical CO₂ laser radiation wave by interaction with a high-power spherical wave (with a different radius of curvature) in a thin layer of gaseous SF₆. The applications of this effect in correction of wave fronts and enhancement of the intensity in phase images are considered.