Dual-band terahertz perfect absorber based on a patterned graphene array with tunable resonance

We present an ultra-thin and dynamically tunable dual-band perfect absorber for the terahertz regime, realized by a patterned graphene array with double-hook subunits. Full-wave numerical simulations demonstrate two distinct absorption peaks within the 3–7 THz range, achieving near-unity absorption rates of 99.96% at 3.6 THz and 99.66% at 4.99 THz. The underlying physical mechanism of this dual-band absorption is rigorously explained using coupled-mode theory (CMT). A key advantage of this design is its active electrical tunability. The absorption peaks can be dynamically shifted by merely adjusting the graphene’s Fermi level, without structural modifications. Furthermore, the symmetric design ensures polarization insensitivity and maintains high absorption under wide-angle incidence (up to 80°). Benefiting from these properties, the device demonstrates outstanding detection capabilities, yielding refractive index sensitivities of 0.74 THz/RIU and 1.10 THz/RIU, respectively. Finally, the design concept is demonstrated to be highly scalable, achieving triple-band absorption functionality through structural expansion, thus providing an attractive platform for multifunctional terahertz devices.