Programmable High-Order OAM-Carrying Beams for Direct-Modulation Wireless Communications

Electromagnetic (EM) beams carrying orbital angular momentum (OAM) are of great importance in modern wireless communications due to their attractive properties of self-reconstruction and multiplexing multiple beams. However, they are hardly deployed in a real-world scenario since they cannot be dynamically generated in a real-time and low-cost way, especially for the case of topological charges more than 2. To resolve this issue, we explore an inexpensive 2-bit programmable coding metasurface working at around 3.2 GHz along with an efficient optimization algorithm for the generation of high-order OAM-carrying beams in a reprogrammable way. Based on the designed metasurface, we can generate OAM EM beams with the electronically controlled vortex centers and topological charges of l = 0, ±1, ±2, ±3, ±4, ±5, and ±6, which have been experimentally verified. As an illustrative example, we demonstrate an interesting application of the designed 2-bit programmable metasurface in direct-modulation line-of-sight wireless communications. We believe that the developed strategy will bring a fundamentally new perspective on the design of wireless communication architectures at various frequencies.