Polarization-insensitive metasurfaces for generating converging vortex beams carrying orbital angular momentum

Abstract

We present the design of novel metasurfaces capable of generating converging vortex beams carrying orbital angular momentum (OAM) at microwave frequencies. Isotropic unit cells are used for constructing such metasurfaces, which allows full phase control of 0 - 2 $\pi$ with high efficiency. Two typical metasurfaces are designed for the generation of converging beams carrying OAM modes l = 1,2. The proposed metasurfaces are polarization-insensitive and can be applied to both linearly or circularly polarized waves.