High‐Efficiency Multi‐Level Beam Switching with Single‐Gate Tunable Metasurfaces Based on Graphene

Abstract The growing demand for ultra‐fast telecommunications, autonomous driving, and futuristic technologies highlights the crucial role of active beam steering at the nanoscale. This is essential for applications like LiDAR, beam‐forming, and holographic displays, especially as devices reduce in form factor. Although a device with active beam‐switching capability is a potential candidate for realizing those applications, there are only a few works to realize beam switching in reconfigurable metasurfaces with active tuning materials. In this paper, a multi‐level beam‐switching dielectric metasurface is theoretically presented with a graphene layer for active tuning, addressing challenges associated with achieving high directivity and diffraction efficiency, and doing so while using a single‐gate setup. For two‐level switching, the directivities reached above 95%, and the diffraction efficiencies are ≈50% at the operation wavelength λ 0 = 8 µm. Through quasi‐normal mode expansion, the physics of the beam‐switching metasurface inverse‐designed by the adjoint method is illustrated, highlighting the role of resonant modes and their response to charge carrier tuning. Under the same design scheme, characteristics of a three‐level and four‐level beam‐switching device is designed and reported, suggesting a possibility of generalizing to multi‐level beam switching.