Ultrawideband hybrid metasurface absorber using VO2 and graphene-based FSS for THz applications

We theoretically propose a hybrid terahertz absorber with dual tunability—thermal via vanadium dioxide (VO2) and electrical via graphene. The proposed design features stacked frequency-selective surfaces and demonstrates ultrabroadband absorption from 1.84 to 8.22 THz (absorption >90%). This can happen under the metallic phase of VO2 (σVO2=2×105 S/m) and chemical potential of graphene (μ) of 0 eV. The absorption amplitude can be dynamically tuned from 8% to 90% by varying VO2 conductivity, thereby highlighting excellent thermal responsiveness. While another narrow channel representing the second mode occurs, when only graphene is active (μ=1 eV), the absorber attains an absorption (>90%) band from 1.25 to 3.67 THz (bandwidth: 2.42 THz). Additionally, the structure supports reconfigurable absorption via graphene tuning and remains effective up to 70° and 60° incidence angles. It is also polarization-insensitive, making it suitable for applications in THz imaging, sensing, communication, and filtering.