A polarization-insensitive broadband metamaterial absorber including a sandwiched graphene material sheet for multitudinous terahertz applications

This research article presents the design technique and characterization of a metamaterial-based broadband multi-layered absorber that functions in the terahertz frequency range and exhibits polarization independence. The suggested absorber is made up of four layers: a gold layer that conducts electricity at the base of the structure, a dielectric layer made of lossy silicon, a graphene layer that acts as a conductor, and finally, an extra gold layer is added for generating resonance and to attain impedance matching between free space and metamaterial. The tunability of the absorption band has been examined by adjusting the Fermi chemical potential and relaxation time of the graphene material. By implementing an appropriate Fermi chemical potential (μ_c) of 0.2 eV and a relaxation time (t_r) of 0.1 ps in the graphene layer, the recommended configuration can attain a broad bandwidth of 2.47 THz (9.42 THz to 11.89 THz) with a fractional bandwidth (FBW) of 23.18 %, maintaining the absorptivity level above 90 %. The proposed design exhibits compact physical dimensions of 20 × 20 μm² and an electrical size of 0.628 λ₀ × 0.628 λ₀, where λ₀ corresponds to the wavelength calculated at the lowest operating frequency. The suggested absorber is effective for multiple terahertz applications, including high-speed communications, imaging, sensing, and environmental monitoring.