Energy flux of a vortex field focused using a secant gradient lens

Abstract

In this paper we simulated the focusing of left circular polarized beam with a second order phase vortex and a second-order cylindrical vector beam by a gradient index Mikaelian lens. It was shown numerically, that there is an area with a negative Poynting vector projection on Z axis, that can be called an area with backward energy flow. Using a cylindrical hole in the output surface of the lens and optimizing it one can obtain a negative flow, which will be situated in the maximum intensity region, unlike to previous papers, in which such backward energy flow regions were situated in a shadow area. Thereby, this lens will work as an “optical magnet”, it will attract Rayleigh particles (with diameter about 1/20 of the wavelength) to its surface.

The optical vortices focusing by subwavelength microelements with variable relief height using high-performance computer systems

“…The Gradient Index (GRIN) materials are used for a number of applications [57][58][59][60][61][62][63][64][65][66] , among which are communication 57,62 , light collimation 63,64 , biological and medical applications [65][66][67] . Gradient refractive index metamaterials can also be used to control acoustic waves 61 , control light propagation in integrated photonic chips 60 , and for sharp focusing 68 . Thus, in this work, we study the diffraction of optical vortices on subwavelength annular gratings with a gradient refractive index of the substrate.…”