Propagation of phase-modulated high-power femtosecond laser pulses in the self-channeling and filamentation mode in air
Yu.E. Geints, A.A. Zemlyanov, O.V. Minina
V.E. Zuev Institute of Atmospheric Optics of Siberian Branch of the Russian Academy of Science, Tomsk, Russia
Keywords: femtosecond laser pulse, phase modulation, self-focusing, filamentation, self-channeling, post-filamentation channel
Abstract
Propagation of high-power phase-modulated femtosecond laser pulses in air is numerically simulated. Spatial modulation of the initial pulse wavefront is carried out using a programmable phase plate consisting of segments arranged in a checkerboard pattern with a variable wave phase jump. The self-focusing, filamentation and post-filamentation channeling of radiation for phase-modulating masks with different phase shifts at the boundaries of neighboring segments are studied within the numerical solution of the nonlinear Schrödinger equation for the time-averaged electric field amplitude. The filamentation domain in air for certain pulse phase modulation types is shown to be significantly shifted (along the coordinate) and elongated compared to an unmodulated pulse. In addition, it is found that the use of phase modulation makes it possible to reduce the angular divergence of high-intensity light channels generated during the post-filamentation propagation stage. This provides a possibility of self-channeling of radiation at distances multiple of the Rayleigh length.
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