Generation of polarization-insensitive perfect vortices by dielectric metasurfaces with diverging or converging axicon phases

Abstract

Perfect vortex (PV) is a special light field with constant annular light intensity distribution while carrying orbital angular momentum. It has been widely used in the fields of optical communications and particle manipulation. However, conventional methods to produce PVs require a series of complex components, which limit their practical use in miniaturization. Here we designed models of PV generators based on highly efficient polarization-insensitive dielectric metasurfaces and smoothly generated PVs in simulation with arbitrarily polarized incident Gaussian beams. Meanwhile, by adjusting the focal length of the lens and the half fan angle of the axicon, ring-shaped focal spots with different radii could be obtained in the propagation space, rendering the system more flexible. By superimposing the phase functions of the four PVs with different ring radii, the coaxial PVs were smoothly generated in simulation. Furthermore, the multi-channel PVs were obtained in simulation by introducing the linear displacement factors. By employing polarization-insensitive dielectric metasurfaces, we believe that this method of PV generation will stimulate further applications in fields such as optical communications, particle trapping and manipulation.