Intensity based measuring of the topological charge alteration by the diffraction of vortex beams from amplitude sinusoidal radial gratings

For convenient optical communications by the aid of vortex beams, topological charge alterations should be translated to the change in intensity of the output light. In this paper, we formulate and experimentally investigate diffraction of vortex beams from amplitude radial gratings having sinusoidal profile. We show that, the diffraction pattern simply renders both topological charge and twist direction of the impinging vortex beam. When, topological charge of the vortex beam and the radial grating spokes number are equal, intensity on the optical axes of the Fraunhofer pattern gets a maximum value. Otherwise, its value on the optical axes remains zero. We examined the method on different vortex beams, the measured topological charge of generated beams are in an excellent agreement with the excepted values. We show that an alteration between two vortex beams, in which one has a topological charge of equal to the grating spokes number, is translated to a binary change in intensity of the output light on the optical axes. This feature might find wide applications in optical communications.

Optical vortices; Diffraction and gratings; Singular optics; Optical communications