Optics and Photonics Society of Iran

Perfect optical vortices (POV) are beams with topological charge that their dark area is independent of topological charge unlike to Laguerre-Gaussian and Bessel-Gaussian beams. In this paper, generation of these beams with different topological charges by Fraunhofer diffraction of Bessel-Gaussian (BG) beam by Laguerre-Gaussian (LG) forked grating was shown. The diameter of POV is independent of its topological charge which is an important property of it. In this study firstly a mathematical expression that describes the BG beam diffraction by LG forked grating is obtained by using Fraunhofer diffraction integral. The results of the analytical solution of the integral indicate the presence of vortex beams with different topological charges in diffraction orders. Numerical simulation of diffraction of various BG beams with different topological charges by forked grating with topological charge , also shows generation of perfect optical vortices in diffraction orders. Interference pattern of a POV and a Gaussian beam demonstrates validity of analytical expression to determine topological charges. Also, in this paper was shown that the topological charge of POV is not dependent upon the size of vortex and order of diffraction.