Numerical Study of High-power Laser Pulse Filamentation in Air at Different Pressure

Nonlinear propagation of high-power femtosecond laser pulses in the filamentation regime in air at different pressures is theoretically studied. Due to scaling laws which relate the density (pressure)of the propagation medium to the initial laser pulse parameters, our study allows for predicting the formation of a nonlinear focus during self-focusing and the formation of a filamentation region on real atmospheric paths hundreds of meters long. The results make it possible to better understand the complex and multifactorial dynamics of the filamentation of powerful ultrashort laser radiation and open up new prospects for optimizing and expanding the range of applications based on this phenomenon, in particular, for remote diagnostics of atmospheric components and energy delivery along long distances. Numerical simulation is carried out on the basis of the reduced (time-integrated) nonlinear Schrodinger equation for the optical field envelope, which governs the nonlinear propagation of high-power femtosecond pulses of a titanium-sapphire laser under conditions of a 16-fold change in air pressure. The formation of the multifocal optical structure in the filamentation region, which is especially evident in these conditions, is considered in detail.