Impact of various mechanisms of the photorefractive effect on polarization singularity generation during the self-focusing of a Gaussian beam in an isotropic medium

Abstract

The emerging of polarization singularity lines (C-lines), accompanying the self-focusing of an initially elliptically polarized Gaussian beam in an isotropic medium with various mechanisms of cubic nonlinearity, is studied numerically. Lines of circular polarization can appear in planes perpendicular to the beam axis as circles centered at the axis in both sub-threshold and super-threshold regimes of nonlinear self-action. The range of beam power values, for which the C-lines are formed, rapidly expands as the initial polarization of the beam gets closer to circular. The radius of the first formed C-line and the distance from the C-line to the border of the medium are decreasing if the beam power increases.