Flexible terahertz metasurfaces with ultra-large incident angle tolerance and mechanical adaptability

Metasurfaces operating under oblique incidence conditions have attracted considerable interest in modern photonic engineering, owing to their capability to enhance angular coverage for next-generation devices including wide-field detectors, multi-angle communication arrays, and advanced radar architectures. However, conventional metasurfaces frequently suffer from limitations in preserving functional stability at high incidence angles, where performance deterioration typically stems from reduced coupling efficiency and phase mismatch. This work proposes flexible terahertz metasurfaces with an ultra-large incident angle, addressing the limitations of conventional metasurfaces that suffer from severe performance degradation under high angles and lack mechanical adaptability. The proposed metasurfaces are designed through the synergistic integration of spoof localized surface plasmons (S-LSPs) and electromagnetically induced transparency (EIT). Experimental results demonstrate that the metasurfaces exhibit polarization-insensitive behavior while maintaining stable transmission spectra under oblique incidence up to 80°. Furthermore, bending tests confirm that the transmission spectrum of the metasurfaces remains stable even under significant mechanical deformation (with a maximum central angle of 111.7°). The proposed flexible metasurfaces provide a novel design paradigm for oblique-incident metasurfaces, holding great potential for emerging applications in conformal terahertz systems and adaptive wearable photonics.