Actively tunable terahertz metasurface absorber due to surface phonon polaritons

Abstract

A tunable terahertz (THz) metasurface (MS) absorber based on the surface phonon polariton (SPhP) is proposed based on a layered structure that consists of a split-silver-ring array followed by a graphene layer, polar crystal layer, and silver layer. A dynamically tunable, polarization-independent, and angle-insensitive MS absorber is numerically investigated at THz frequencies. By changing the Fermi energy of graphene from 0 to 1.0 eV, the state of the absorber can switch between the OFF state (with an absorptivity above 90%) and ON state (with an absorptance below 3%). The switching intensity (SI) of the absorber remains greater than 80% for TE incidence wave with incident angles from 0° to 70° and for TM incidence wave incident angles from 0° to 40° in the frequency range from 2.74 to 3.51 THz. These results should be helpful in guiding the design of THz tunable devices such as optical switches, smart absorbers, and imaging.