Generation of periodic filament arrays by self-focusing of highly elliptical ultrashort pulsed laser beams

This paper demonstrates that powerful highly elliptical ultrashort pulsed laser beam, launched into a fused silica sample, spontaneously breaks-up into periodic one- and two-dimensional arrays of regularly spaced multiple filaments with high shot-to-shot reproducibility. Periodic MF structures evolve along the long axis of the beam, and their period is controlled via the input beam intensity. The experimental results we reproduced in detail by the numerical simulations of the nonlinear Schrodinger equation (NLSE) in the continuous-wave and ultrashort pulse limit and by means of the analytical model, which explains multiple filamentation as a sole result of the phase-matched multistep four-wave parametric interactions occurring in the self-focusing elliptical laser beam.