An ultra-broadband and thermally tunable terahertz metamaterial absorber with high fabrication tolerance

Terahertz (THz) broadband absorbers with high efficiency and tunability are crucial for applications in electromagnetic shielding, sensing, stealth technology, and THz communication systems. In this work, an ultra-broadband, thermally tunable THz absorber with high fabrication tolerance is proposed based on the phase-change material vanadium dioxide (VO₂). The absorber adopts a metal-dielectric-metal (MDM) configuration, consisting of a gold reflective layer, a SiO₂ dielectric spacer, and a patterned VO₂ top layer. When VO₂ is in the metallic phase, the absorber achieves absorptance exceeding 90% over the frequency range of 3.1-10.0 THz, with a large fractional bandwidth of 105.34%. The broadband absorption mechanism is revealed through impedance matching analysis, multiple reflection interference theory, electric-field distribution analysis, and multipole decomposition. The results show that the absorption is primarily driven by electric dipole resonance, with contributions from toroidal and magnetic dipole resonances, which effectively confine electromagnetic energy and suppress reflection. Thermal modulation of the VO₂ phase transition enables dynamic tunability of the absorption response, while parametric and structural-shape analyses confirm excellent fabrication tolerance. This work demonstrates that the proposed VO₂-based metamaterial absorber provides a practical solution for advanced THz functional devices, combining high efficiency, broadband performance, and robust fabrication compatibility.