Bending Sensing Based on Quasi Bound States in the Continuum in Flexible Terahertz Metasurface

Abstract Bound states in the continuum (BIC) promote strong interaction between light and matter, which has been introduced into the metasurfaces to achieve ultra‐high Q resonance and provide a powerful tool for high‐sensitivity sensing. At present, BIC‐based sensors have been applied in biological and chemical sensing. Here, their application in bending sensing is investigated. BIC is employed to design the terahertz metallic metasurfaces and propose a feasible method for the high‐ Q sensitivity detection of micro‐bending. It is demonstrated theoretically and experimentally that BIC can transform into an observable quasi‐BIC by tuning the structural parameters. More importantly, it is the first report to investigate the bending sensing performance of BIC metallic metasurfaces. The experimental results verify that both metasurfaces supporting symmetry‐protected BIC and parameter‐tuned BIC are sensitive to changes in curvatures. It indicates that the designed BIC metasurfaces can realize the bending deformation detection of some precision instruments. These results expand the application of BIC‐based sensors in the sensing field. It is expected that the design can find potential applications in wearable photonic devices, intelligent robots, and bionic machines.