Transformation of singular light beam transverse structure in resonant media

Abstract

535.34The peculiarities of transformation of transverse structure for singular light beams propagating in a resonant medium have been analyzed theoretically. The influence of nonlinear absorption, self-focusing, and defocusing on the characteristics of optical vortices with different topological structure has been studied. The formation conditions and parameters for singular spatially localized structures have been characterized. Introduction.A screw dislocation of a light-beam wave front appears as a screw surface with a special point at which the field amplitude is equal to zero and the phase is undefined [1]. A phase shift in multiples of 2π occurs if this singularity is avoided. Light beams with wave-front dislocations (optical vortices) that are observed in optical fields with a complex transverse structure [2] and in laser cavities [3] or are produced as a result of light diffraction on computer synthesized holograms [4] are constantly of interest to researchers because of numerous potential applications.The propagation of singular light beams in nonlinear media is investigated in order to find the stability conditions of their transverse and topological structure [5,6], to study the waveguide properties of transverse localized optical vortices in media with different types of nonlinearity [7-9], to analyze their polarization structure [10], and to develop methods for transforming the topological structure through nonlinear interactions [11,12]. Transformation of the transverse structure of Bessel light beams in various nonlinear materials is widely investigated together with singular beams [13][14][15].Herein features of the transformation of the transverse structure of singular light beams with the combined influence of nonlinear absorption and self-focusing (defocusing) of the radiation in resonant media are analyzed and the conditions for forming localized transverse structures as dark soliton vortices are determined. The model of resonant media that is used is suitable for describing the interaction of radiation with dye solutions and with activated crystals, crystals with color centers, and vapors of complex organic compounds.Theoretical Model of the Propagation of Singular Light Beams in Resonant Media. The propagation of singular light beams in resonant media will be investigated using a truncated wave equation for the complex amplitude of field E of the form [16]:

Wave front transformation of optical vortices with multiwave interactions in resonant media

“…Thus, for example, self focussing (defocussing) effects, which show up when the intensity of a light beam is comparable to the saturation intensity of a resonant transition, lead to the formation of localized spatial structures in the form of dark solitons [9]. The processing of light fields by nonlinear interference and holographic techniques based on multiwave interactions in resonant media [10] also offers some promise for solving problems involving transformation of the wave fronts of vortical optical beams.…”