Simulation of femtosecond laser pulses self-focusing with normal dispersion in air by the method of diffraction-beam tubes
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, 1, Academician Zuev square, Tomsk, 634055, Russia
Keywords: фемтосекундные лазерные импульсы, самофокусировка, филаментация, дифракционно-лучевая трубка, нормальная дисперсия, femtosecond laser pulses, self-focusing, filamentation, diffraction-beam tube, normal dispersion
Abstract
Based on the numerical simulation and qualitative analysis, the effect of the group velocity dispersion on the formation of light structures during self-focusing and filamentation of femtosecond titanium-sapphire laser pulses in air was studied. It was found that dispersion occurs when the dispersion length is not the smallest process scale. Based on the results of numerical solutions of the nonlinear Schrödinger equation in a Kerr-plasma dissipative dispersion medium using the method of diffraction-beam tubes, the main regularities of filamentation of femtosecond laser pulses in air at various pulse durations, initial beam radii, and peak emission powers were determined. It was shown that the relative (normalized to Rayleigh length) coordinate of the beginning of filamentation increases with increasing the dispersion distortion of the pulse. The length of the filamentation channel is reduced. For shorter laser pulses (tens of femtoseconds) the filamentation failure is observed, when the laser beam radius is increased. For this class of pulses, an increase in the size of the energy replenishing diffraction-beam tube occurs, and the angular divergence of the post-filamentation light channels also increases.
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