Design and Simulation of a High-Efficiency Tunable Terahertz Absorber Based on Patterned Graphene

The rapid expansion of terahertz (THz) communication, nondestructive testing and biosensing puts forward urgent demands for absorbers with switchable working bandwidth, yet parts of existing graphene-based absorbers adopt costly noble-metal backplanes and can hardly realize reversible narrow and broadband absorption conversion. In this work, a three-layer metamaterial absorber is designed, where low-cost tungsten replaces precious metals as reflective substrate, polyimide serves as intermediate dielectric and patterned graphene composes the top absorbing layer. The finite element method (FEM) is employed to investigate the synergistic modulation of THz absorption characteristics by graphene's Fermi level (E_f) and relaxation time (τ) across the 0-6 THz frequency range. Simulation results reveal that increasing E_f from 0.1 eV to 0.9 eV effectively broadens the effective absorption range. At fixed E_f = 0.9 eV, dual discrete absorption peaks with peak absorptivity up to 99.8% emerge at τ = 0.1 ps, while reducing τ to 0.05 ps enables an ultrawide 2.5 THz high-efficiency absorption band (absorptivity ≥ 90%) including a 1.4 THz near-perfect absorption (absorptivity ≥ 99%) region. Benefiting from high geometric symmetry, the proposed structure exhibits polarization-insensitive absorption and stable performance for incident angles up to 60°. This numerical work provides design references for low-cost switchable THz absorbers.