Generating elliptic perfect optical vortex beams with efficient dielectric metasurface in the ultraviolet spectrum

Abstract

Due to the helical phase profile as well as the topological charge-independent doughnut spatial structure, perfect vortex beams have attract attentions in fiber communications and particle manipulations. However, for some advanced applications such as optical cage and optical microfluidic sorting and acceleration, it is more meaningful to generate asymmetric optical vortex fields such as elliptic perfect optical vortex (EPOV) beams. Herein we utilize silicon nitride nanopillars, functioning as half-wave plates, to construct high-efficiency geometric phase metasurfaces for the generation of EPOV beams with the integer and fractional topological charges in the ultraviolet range. By adjusting scaling factor, the shape of beams can be freely changed from circle to ellipse. In addition, multi-channel EPOV beams with arbitrary shape and different topological charges are produced with the help of the superposition principle of phase in Fourier space. We envision that this ultraviolet metasurface-based generator of EPOV beams can be used for manipulation of microscopic particle along an ellipse with acceleration and for the generation OAM-entangled photons.