Gaussian lenses initiate optical vortices in laser beams during self-action in Kerr-like medium

摘要

It is shown that Gaussian lenses initiate closed line of dislocations in coherent beams with initially smooth wavefront. The stigmatic lenses originate the circle line of edge dislocation, situated on the beam cross-section. In the case of astigmatic Gaussian lens this closed curve gets out from the plane and a quadruple of alternate single-charged optical vortices is born and annihilates in the beam cross-section. The distribution of topological charge signs in the quadruple along z axis is defined by focusing or defocusing type of Gaussian lens. The model of Gaussian lenses explains self-action of fundamental mode laser beams transmitted by Kerr-like media. Two methods were used for study of optical singularities appearance: the geometrical optics analysis for rapid qualitative location and numerical modeling of Kirchhoff-Fresnel integral for exact solution.