Spatial structure of femtosecond laser radiation during filamentation in air
D.V. Apeximov, Yu.E. Geints, A.A. Zemlyanov, A.N. Iglakova, A.M. Kabanov, O.I. Kuchinskaya, G.G. Matvienko, O.V. Minina, V.K. Oshlakov, A.V. Petrov
V.E. Zuev Institute of Atmospheric Optics of Siberian Branch of the Russian Academy of Science, Tomsk, Russia
Keywords: femtosecond laser pulse, air, filamentation, light channels, diffraction-ray tube
Abstract
The results of experimental and theoretical studies of the evolution of the small-scale transverse structure of high-power femtosecond laser radiation propagating in air in the multiple filamentation mode are presented. It has been found that the presence of intensity inhomogeneities in the initial transverse profile of a laser beam leads to the formation of high-intensity light channels due to the Kerr-induced self-focusing effect. When the power in these channels exceeds a certain threshold value (the critical power), the filamentation in these structures is implemented. Parameters of these light channels are theoretically estimated on the basis of the diffraction-ray model of single filamentation. It is shown that the initial radius of intensity inhomogeneities in the transverse profile of a laser beam with a centimeter radius and subterawatt power is of characteristic value of several millimeters.
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