A broadband, polarization-selective and complementary absorber for hybrid terahertz structure

Abstract The tunability of graphene and the phase transition property of vanadium dioxide (VO 2 ) enable dynamically tunable absorption in the terahertz frequency band. In this study, we propose a terahertz (THz) absorber comprising graphene hollow-patterned layers, a silver grating layer and dielectric/VO 2 layers. The design significantly broadens the absorption bandwidth through plasmon coupling and mode hybridization. When the graphene Fermi level is 0.9 eV and VO 2 is in its metallic phase, the structure maintains over 90% absorption from 5.65 to 9.30 THz for normal incidence of TE-polarization, while exhibiting high reflectivity for normal incidence of TM-polarization. The absorption of TE wave is tuned from nearly 100% to 20% or 30% either by lowering the graphene Fermi level to 0.1 eV or by adjusting the VO 2 conductivity to its insulating phase. Additionally, adjusting the incident elevation angle θ and azimuth angle φ enables complementary wave absorption-reflection responses for TE and TM waves. Specifically, at φ = 90°, the structure absorbs TE wave and reflects TM wave over a θ range of 0° ∼ 45°; at φ = 0°, it reflects TE wave and absorbs TM wave retained for θ of 0° ~ 60°.