Brillouin zone folding-driven multi-QBIC metasurfaces for enhanced trace analyte identification

The high Q factors and local field enhancement effect of bound states in the continuum (BIC) resonances offer significant potential for detecting trace substances. However, conventional BIC-based metasurface sensors suffer from material loss-induced low Q factors, limited field enhancement, and the constraint of a single resonance mode on the metasurface. Here, a Brillouin-zone-folding-driven metasurface supporting multiple quasi-BIC (QBIC) resonances is introduced to improve the detection performance of trace analytes. By folding resonance modes below the light cone to Γ point and then breaking the structural symmetry to leak these resonance modes into free space, multiple QBIC resonances are excited on a single device. In experiments, different trace analytes were individually loaded onto metasurfaces, and their transmission spectra were subsequently processed using a support vector machine model for identification. Simultaneous increases in the Q factor and field enhancement improve sensitivity, while multi-resonance excitation enables frequency-multiplexed synergistic analysis, thereby improving identification accuracy. Overall, this work presents an integrated approach that simultaneously elevates the sensitivity and accuracy of trace analyte identification and establishes a scalable pathway toward compact multi-resonance devices.