Numerical study of laser filamentation of high-power femtosecond pulses in air of different pressures
Yu.E. Geints1,2, O.V. Minina1,2
1V.E. Zuev Institute of Atmospheric Optics of Siberian Branch of the Russian Academy of Science, Tomsk, Russia
2Russian University of Transport (MIIT), Moscow, Russia
Keywords: femtosecond laser pulse, nonlinear focus, self-focusing, laser filamentation, pressured gas, laser beam structure
Abstract
The propagation of high-power femtosecond laser pulses under conditions of their filamentation in air of different pressures is theoretically studied. This approach allows predicting the formation of a nonlinear focus during self-focusing and the filamentation domain on real atmospheric paths hundreds of meters long. This is possible due to the scaling laws that relate the pressure in a propagation medium to the initial parameters of high-power ultrashort laser pulses. Thus, the results of laboratory studies under conditions of increased pressure at distances of several meters are transformed into extended air paths hundreds of meters long at atmospheric pressure. The results allow better understanding of the complex and multifactorial dynamics of filamentation of high-power ultrashort laser radiation and open up new prospects for optimizing and expanding the range of applications based on this phenomenon, in particular, remote diagnostics of atmospheric components and long-range energy delivery. Numerical simulation in this work was performed based on the reduced (time-integrated) nonlinear Schrödinger equation for the optical field envelope during propagation of high-power femtosecond pulses of a titanium-sapphire laser under conditions of a 16-fold change in air pressure. The formation of a multifocal structure of the filamentation domain, which is especially evident under these conditions, is considered in detail.
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