ИСТИНА

Inhomogeneously polarized monochromatic electromagnetic fields may contain lines of circular polarization also known as lines of polarization singularity (C-lines). In paraxial beams, the intersections of the C-lines with the plane transversal to the propagation direction are treated as C-points. The C-point is also characterized by its topological index, which is the number of full rotations of the polarization ellipse on a counterclockwise loop around the C-point. It could be 1/2 (180°-rotation), -1/2, or higher numbers, divisible by 1/2. We have theoretically studied in the first time the interaction of two collinear specific-kind monochromatic beams with polarization singularities in the nonlinear isotropic gyrotropic medium. The relations between the components of local and nonlocal cubic optical susceptibility tensors determine possible scenario of the interaction of circularly polarized components of the light field. The processes of pairwise creation and annihilation of the C-points with opposite topological charges in the bulk of the nonlinear medium were observed. The sum of the topological charges of all of the C-points in the transversal section of the propagating light remains constant as the propagation coordinate changes. The nonlinearity of the medium plays key role in the scenario of the evolution of the C-points. In case of the mutual focusing of the circularly polarized components of the light field the increase of the intensity of the incident beams leads to the retardation of the interaction of the C-points. In case of the mutual defocusing of the circularly polarized components of the propagating light, the bigger is the intensity of the incident beams, the faster the processes of pairwise creation (or annihilation) go.