Broadband tunable coding metasurfaces based on a metal patch and graphene for beam control at the terahertz frequencies.

We present a broadband tunable coding metasurfaces structure using a cruciate metal patch and circular graphene on a multilayer substrate. By changing the Fermi level of the graphene, we can achieve obvious reflection phase variation to design multi-bit coding metasurfaces. In the research of 1-bit coding metasurfaces, we combine the advantages of graphene and copper to realize the real-time adjustment of the reflected waves in four broadband frequency bands. In this case, we can control the number of far-field reflected waves in the frequency range of 5.45-6.45 THz. Then, we create 2-bit and 3-bit coding modes on the basis of 1-bit coding metasurfaces to obtain a single beam of reflected waves. Finally, we use the convolution calculation to realize the real-time adjustment of the single beam reflection direction from 0° to 360° in the azimuthal plane. Research of the 2-bit and 3-bit coding modes also provides a way to control the number and direction of the reflected beam, specifically in the 1-bit coding mode. The present coding metasurfaces structure provides inspiration for the design of functional devices in future-oriented intelligent communication.