A Free-Space Orbital Angular Momentum Multiplexing Communication System Based on a Metasurface

Optical vortex beams carrying orbital angular momentum (OAM) have received great attention since the 1990s. In particular, OAM offers an additional degree of freedom, thus, enabling boosting of data transmission capacity in communication systems. One of the major challenges of OAM-based communication lies in multiplexing OAM via a kind of effective, compact, and flexible approach. Here, a novel approach to achieve the generation and combination of OAM beams by a pre-engineered reflective metasurface chip is demonstrated. Compared to traditional methods of OAM generation, this approach shows superiorities of broadband operating wavelength, high mode purity, flexible design, and compact size. Moreover, a free-space OAM multiplexing communication experiment based on the single metasurface is successfully carried out, performing 448 Gbit s⁻¹ data transmission with four different topological charges of OAM and two polarizations by 28-GBaud QPSK signals. This work experimentally demonstrates promising applications of the metasurface in high-capacity optical communication systems.