Design of graphene-based terahertz metasurface for reconfigurable wavefront manipulations

The resonant phase of metasurface, incorporating the geometric phase and propagation phase, has become one of the most effective methodologies to control the electromagnetic wavefronts. In this study, we numerically propose a graphene-based reflective metasurface that employs the resonant phases for terahertz (THz) wavefront control. The metasurface consists of a one-dimensional (1D) graphene grating, a silicon dioxide spacer, and a gold back mirror, which form a Fabry-Perot-type resonant cavity. By tuning the grating width, we achieve precise 0-2\pi phase control, enabling THz beam deflection and focusing. By further introducing electrical doping to change the Fermi level of the graphene grating, we can realize dynamic phase modulation through a directly applied electrical bias. As a result, the electrically tunable metasurface supports continuously adjustable beam steering and focal lengths without altering its physical structure. These results demonstrate the metasurface's potential for reconfigurable and compact THz photonic devices.