Single-Layer Reflective Metasurface for Dual-Band OAM Multiplexing

Abstract

In this paper, a general scheme is proposed for dual-band orbital angular momentum (OAM) multiplexing based on a single-layer reflective geometric metasurface. As an OAM multiplexer, the proposed metasurface can distinguish different incidences featuring different incident angles, transform them into OAM waves with different topological charges (TCs) and control their reflection angle by modifying the k-space of the incidences simultaneously. In this way, the incidences can be combined into a coaxial beam without mutual interference because of the inherent orthogonality of different OAM modes. To achieve dual-band OAM multiplexing, a single-layer metal-insulator-metal (MIM) meta-atom that can independently impose arbitrary phase profiles on incidences at two different frequencies is designed. Based on it, a geometric metasurface is proposed for multiplexing OAM waves at 7 GHz and 14 GHz simultaneously. The simulated results show that eight independent data channels are created in a broadside beam when eight off-axis incidences carrying different information impinge on the proposed metasurface. This phenomenon indicates that the proposed metasurface can effectively achieve multiplexing by combining frequency and OAM domains to boost the channel capacity in wireless communications.