Actively tunable terahertz metasurface absorber due to surface phonon polaritons

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 degrees to 70 degrees and for TM incidence wave incident angles from 0 degrees to 40 degrees 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. (C) 2022 Optica Publishing Group