Transformation of the spatial spectrum of optical radiation in parametric processes

An investigation was made of the transformation of the spatial spectrum of optical radiation as a result of passage through an excited nonlinear medium. Experiments confirmed that, under certain conditions, this medium reemitted the energy of a plane wave of the incident radiation in the form of side spatial frequencies, whose spectrum corresponded to the autocorrelation function of the spatial spectrum of the pump radiation. Two models of parametric processes were used to account for the observed effect. The effect should be useful in investigations of spatially modulated radiation traveling across a phase-distorting medium.