Radiation transfer model of self-trapping spatially incoherent radiation by nonlinear media

We modify the radiation transfer approach, accounting for refraction, and apply this model to the analysis of propagation of spatially incoherent beams in inertial nonlinear media. For double Gaussian beams, an oscillatory regime of nonlinear diffraction is revealed. An explicit analysis of the oscillations was carried out for logarithmic saturating nonlinearity. We show that "big incoherent solitons," which possess an arbitrary transverse profile of intensity and exist for a wide class of nonlinear media, are steady state solutions of the radiation transfer equation. [S0031-9007(98)07197-X].