Design, fabrication, and measurement of an anisotropic holographic metasurface for generating vortex beams carrying orbital angular momentum

In this Letter, to the best of our knowledge, a novel anisotropic surface impedance holographic metasurface antenna for generating orbital angular momentum (OAM) is developed through design, fabrication, and measurement at radio frequencies. The classical leaky-wave theory and a microwave holography method are combined to realize vortex waves carrying different OAM modes flexibly. The holographic metasurface composed of subwavelength quasi-periodic anisotropic metallic patches on a grounded dielectric substrate operates by exciting the interference patterns. The interferences are generated between a reference wave excited by the monopole antenna and a field with the desirably shaped wavefront-carrying helical phase. Numerical simulation has shown good agreement with the experimental results, which lays a solid foundation for holographic metasurface antennas having the potential for OAM generation at radio frequencies.