Theoretical investigation of a VO2-based curved metastructure absorber with hyperbolic paraboloid geometry for ultra-broadband terahertz absorption

A novel design strategy, which achieves significant broadening of the absorption bandwidth by transforming traditional planar layered metastructure absorbers (MAs) into curved surface configurations, is proposed. The initial planar-structured device is composed of top/lower vanadium dioxide (VO₂) resonant layers, a polyimide dielectric layer, and a metal reflective substrate. Then, a hyperbolic paraboloid geometry is introduced to expand the absorption bandwidth through surface curvature modification, with a systematic investigation of the curvature magnitude's impact on absorption performance. Finally, the absorption bandwidth is further optimized by extending the unit cell of MAs into a 2 × 2 array and implementing a gradient sinking method. The obtained results demonstrate that the given MA maintains an absorption rate above 90% within the frequency range of 0.187–10.000 terahertz (THz), achieving a relative bandwidth of 192.66%, alongside a low radar cross-section (RCS). This study provides an innovative solution for ultra-broadband MA design, demonstrating significant application potential in next-generation radar systems and high-sensitivity detection technologies.