Diffraction-ray optics of femtosecond laser pulses under normal dispersion conditions in air

The results of a theoretical study of the propagation of femtosecond pulses of a Ti:Sa laser under normal dispersion conditions in air are presented. The use of the diffraction-beam tube method for the analysis of numerical solutions of the nonlinear Schrödinger equation in a dispersion medium with Kerr-plasma nonlinearity made it possible to determine the basic regularities of femtosecond laser pulses self-focusing and filamentation in air at various pulse lengths, initial beam radius, and peak powers. It is shown that in the case of the group velocity dispersion influence with an increase in the initial laser beam radius, the filamentation breaks down even at large supercritical powers. It is shown that with an increase in the dispersion distortions of the pulse the radius of the energetically replenishing diffraction beam tube, the angular divergence of the post-filamentation light channel, and the nonlinear focus coordinate normalized to the Rayleigh length for the central time layers of the laser pulse and the integral picture are increasing.