Theory of second-harmonic generation in strongly scattering media

Abstract

Second-harmonic generation is studied in a medium which is both nonlinear and disordered. Disorder-induced strong elastic scattering of both a fundamental and second-harmonic light gives rise to a diffusionlike regime of light propagation. The interference effects, which cannot be described by the diffusion approximation, are taken into account. They are shown to lead to a sharp peak in the angular distribution of second-harmonic intensity. The direction of the maximum second-harmonic intensity is found to be roughly opposite to the one determined by the usual phase-matching condition in an effective transparent medium. Different models of disorder are considered, and the corresponding values of peak-to-background ratio are calculated.