Polarization-Insensitive Terahertz Tunable Broadband Metamaterial Absorber on U-shaped Graphene Array

In this paper, we propose a broadband metamaterial absorber developed on a simple periodic structure of a U-shaped graphene array that could offer polarization-insensitive wideband terahertz absorption with configurable active tuning. Simulation results reveal that when the graphene's electrochemical potential or Fermi energy was adjusted to 0.7 eV, the bandwidth with absorption greater than 90% is approximately 3.03 THz for transverse electric polarization and 4.3 THz for transverse magnetic polarization while the maximum absorption is greater than 80%. In addition, when the graphene relaxation period is extended from 0.1 ps to 0.5 ps, the same structure functions as a five-band metamaterial absorber with a peak absorption of greater than 90%. Furthermore, the claimed metamaterial absorber provides polarization-insensitive characteristics and retains a high capacity for absorbing both polarized terahertz waves whenever the angle of incidence is less than 40°.