Two-dimensional tunable polarization-dependent absorptions for binary and ternary coding

Polarization coding is of great importance because of its applicability to information processing, storage, and security devices. In this paper, we numerically demonstrated a binary and ternary polarization coding scheme using a cross-shaped graphene/Au hybrid metasurface with two-dimensional (2D) electrical tunability. The C₄ symmetry broken of the cross-shaped structure, caused by different lengths of Au bars in x-and y-directions, allows 2D tunability for x-and y-polarized waves at one biasing condition. For x-polarized wave incidence, the proposed structure generates near-zero or near-unit absorption by switching the graphene's Fermi energies, corresponding to the binary codes of '0' and '1'. Due to 2D tunability, the combination of two absorptions excited by x-and y-polarized waves at 2.45 THz are encoded into ternary codes with the states of '-1', '0', or '1' by gating voltages. The compatibility for binary and ternary coding in the tunable metasurface opposes huge potentials in artificial intelligent devices.