Miniaturized Reflection-Type Metasurface for Generating High-Purity Vortex Beams

By utilizing Pancharatnam-Berry phase concept, a bow-tie shaped reflection-type metasurface array in this work is proposed for generating high-purity vortex beams. The miniaturized reflective metasurface unit cell is designed for covering the frequency bandwidth range from 10.27GHz to 19.44GHz. The incident plane waves can be converted into vortex waves carrying orbital angular momentum by the unit surface, which keeps a more than 90% polarization conversion efficiency in working bandwidth. In compare with other metasurface unit cells, the designed bow-tie shaped structure has the advantages of high conversion efficiency, small size and broad bandwidth. The reflective arrays are designed for generating the vortex beams with the topological charge of -1, -2 and -3, which are constructed by rotating meta-atoms. The corresponding energy weight analysis and near-field electric field distribution of each reflected vortex wave are achieved by numerical simulation to verify the high performance of the designed metasurface. This paper shows that the proposed metasurface array can generate stable and high-purity vortex beam in the whole bandwidth.