Topological Charge Of Optical Vortex Research Articles

Atmospheric propagation of gradient-shaped and spinning femtosecond light pulses

The multiple filamentation of high power, ultrashort laser pulses is investigated for special waveforms exhibiting either sharp intensity gradients or vortex shapes having an angular orbital momentum. First, theoretical estimates are established on the basis of a (2+1)-dimensional model discarding temporal dependences, in order to evaluate the number of filaments and their onset distance with respect to the peak beam power or with the topological charge of optical vortices. Numerical simulations are next performed from this model and they confirm the theoretical expectations, at least qualitatively. These are shown to hold in (3+1)-dimensional geometry involving time variations, through direct numerical integrations of the propagation equations.

Computation of topological charges of optical vortices via nondegenerate four-wave mixing

In this paper, we report an experiment, which demonstrates computation of topological charges of two optical vortices via non-degenerate four-wave-mixing process. We show that the output signal beam carries orbital angular momentum which equals to the subtraction of the orbital angular momenta of the probe light and the backward pump light. The ⁸⁵Rb atoms are used as the nonlinear medium, which transfer the orbital angular momenta of lights.

The relationship between topological characteristics of component vortices and polarization singularities

It is shown theoretically and experimentally that the total topological charge of optical vortices associated with linearly polarized orthogonal components and positioned on, s-contours bounding some field's area is equal to the doubled total topological index of C-points located in this area. This conclusion is valid also for field regions, which contain areas with different kind of polarization (left- or right-hand) independently on the number and structure of such areas.

Conversion of topological charge of optical vortices in a parametric frequency converter

It is shown that sum-frequency generation of light beams with vortices allows to construct vortices of different topological charges. An optical parametric amplifier enables to produce a vortex with opposite topological charge (to the reverse vortex). In this way, a frequency converter can be seen as a prototype of an optical processor which allows to produce simple arithmetical operations with topological charges of the interacting vortices.