双裂环超表面中高Q值连续域束缚态及传感应用研究

<p indent="0mm">Bound states in the continuum (BICs) are a unique physical phenomenon, located within the continuous spectrum yet completely decoupled from the radiation pattern. They are widely used in the design of metasurface with high quality factors. An innovative symmetric metal split-ring metasurface structure capable of realizing multiple tunable BICs is proposed. This metasurface periodic structural unit consists of a silica substrate and two mirror-symmetric metal split-rings. The application of optical sensing is also investigated in detail. By breaking the symmetry of the metasurface structure, the intrinsic LC resonance and radiation modes are no longer perfectly orthogonal to each other. As a result, quasi-bound states in the continuum (Quasi-BICs) with very narrow resonance linewidths and very high quality factors are obtained due to radiation leakage, achieving a quality factor (<italic>Q</italic> value) that can reach up to 18019. To deeply understand this evolution process, a theoretical analysis using coupled mode theory is conducted in this paper. The results demonstrate a high degree of consistency between numerical simulations and theoretical predictions. Moreover, the narrow resonance linewidth and high quality factor provide a solid theoretical foundation for their application in sensing. It was found that the symmetry-protected Quasi-BICs generated on its surface possess high sensitivity values up to <sc>140 GHz/RIU</sc>. Based on this sensing study, a microchannel was designed using a PMMA media layer. The sensing properties of liquids with different refractive indices flowing through the uncovered portion were investigated, showing sensitivity up to <sc>−108.3 GHz/RIU</sc>. Subsequently, due to the sensitivity of BICs to spatial perturbations, the effect of medium surface roughness on the Quasi-BICs properties of the metasurface was also investigated. The sensing sensitivities of convex/concave surfaces were <sc>0.156</sc> and <sc>0.214 mm⁻¹,</sc> respectively. The findings of this research are expected to provide a theoretical basis for designing and developing multifunctional high-sensitivity sensor devices.