Femtosecond-terawatt laser pulses in air: Formation of multiple filaments

Abstract

A theoretical investigation of ultrashort pulse propagation in various transparent media has been carried out. It is based on the numerical solution of the optical wave equation, taking into account nonlinear effects, leading to a nonlinear Schrödinger equation in dimensionless variables. In particular the multiple filament formation is calculated using a plane wave linear perturbation model in a medium free of dispersion. The results show a new propagation regime: the breakup of an ultrashort laser beam, beyond 50 – 100 “critical powers”, into multiple filaments at relative low peak intensities in the filaments (1011–1012 W/cm^2) and, hence, minor plasma generation. The numerical simulations are in good agreement with experimental measurements.