Polarization-insensitive ultra-broadband terahertz metamaterial absorber using vanadium dioxide and graphene

Metamaterial broadband absorbers have attracted significant attention due to their unique ability to manipulate electromagnetic waves in the terahertz (THz) regime. In this study, a thermally tunable ultra-broadband THz absorber is proposed by integrating patterned vanadium dioxide (

) and graphene. Leveraging the reversible phase-transition characteristics of

, the absorber enables dynamic switching between ultra-broadband and multi-band absorption modes. In the metallic phase, the absorber exhibits a remarkable absorption bandwidth ranging from 4.08 to 35.25 THz, exceeding most previously reported THz absorbers. The absorption intensity can be continuously tuned from 8.4% to 99.9% through thermal modulation. Owing to its symmetric design, the absorber demonstrates polarization insensitivity and maintains an average absorption above 85% under oblique incidence up to ${60}^{\circ }$. Furthermore, the absorption performance remains robust against variations in ambient refractive index. The proposed absorber holds strong potential for advanced applications in electromagnetic stealth, biomedical imaging, and terahertz sensing systems.