Spatial coherence of radiation in conditions of small-scale self-focusing

A numerical analysis of linearized equations for spatial correlation functions of fluctuations of an intense light wave in a medium with cubic nonlinearity is presented. It is shown that, irrespective of the type of initial perturbations (amplitude or phase), the variance of the fluctuations increases monotonically with distance in conditions of self-focusing. This increase is the result of energy transfer from the regular part of the light wave to the part fluctuating due to the nonlinearity.