Graphene-Based Reconfigurable THz Metasurface with Independent Control in Both Orthogonal Polarizations

This paper presents the design and simulated performance evaluation of an anisotropic electrically reconfigurable THz metasurface (MS) that provides reflection phase and magnitude control, independently, on each of the two orthogonal linear polarizations. The MS unit cell comprises two graphene monolayers, one patterned in a ribbon and the other in an H-shaped patch, orthogonally arranged, individually addressed, and separated by a SiO${}_2$ spacer on a silicon substrate backed by a gold mirror. We initially employ electromagnetic theory to develop an equivalent circuit and transmission line model that can be used to accurately analyze a given structure or to initialize the design parameters. Subsequently, we optimize the unit cell design via full-wave simulations, and validate the developed model, finding good agreement. The achieved reflection phase tuning is ${180}^{\circ }$ with $-3$ dB reflection magnitude for both y- and x-polarized illumination, near the resonant frequency of 0.75 THz. The MS is also capable of reflection magnitude tuning, ranging from high reflection to high absorption, reaching approximately $-25$ dB and $-10$ dB for the y- and x-polarized illumination, respectively. Such reconfigurable THz metasurfaces, with independent and decoupled control in both polarization channels, offer benefits for next-generation wireless communication, imaging, holography, and sensing.