Multiple scattering, modulation instability, and filamentation of a femtosecond laser pulse in a dispersion medium

Based on the stratified model of multiple coherent scattering of radiation in a dispersion medium, the nonlinear problem of the multiple filamentation of femtosecond laser pulses is studied by the Monte-Carlo method. It is shown that the modulation instability of a high-power light field, which develops on perturbations appearing upon coherent scattering by particles, causes the stochastic breakup of the pulse into numerous filaments. The influence of the size and concentration of particles in water aerosol on the generation of filamentation in a laser pulse is statistically estimated and the regions of different filamentation regimes are determined. The dynamic picture of the evolution of multiple filamentation and formation of plasma channels due to multiphoton ionisation upon aerosol scattering is obtained.