Simulation of Self-Focusing of Femtosecond Laser Pulses in Air by the Method of Diffraction-Beam Tubes

Abstract

Results of the theoretical study of the propagation of femtosecond pulses of a Ti:Sapphire laser in air under self-focusing and filamentation are presented. The self-focusing of laser pulses is analyzed on the basis of the method of diffraction-beam tubes. The analysis established that specific light structures were formed in a laser beam during self-focusing. One of such structures is an energy-replenishing diffraction-beam tube, which provides the necessary energy for filamentation and has the form of a high-intensity light channel during postfilamentation pulse propagation. The dependences of the radius and power of the energy-replenishing tube on the initial beam radius and peak power at a fixed pulse length are derived. It is revealed that the energy consumption of radiation for the filamentation decreases with an increase in the beam radius. The peak power contained in the energy-replenishing light tube during the postfilamentation laser pulse propagation does not exceed the critical self-focusing power of a Gaussian beam and weakly depends on the initial pulse parameters.