Dual quasi-bound states in the continuum enabled non-dispersive infrared gas sensing

In this paper, we demonstrate a symmetry-engineered dielectric metasurface supporting dual quasi-bound states in the continuum (QBICs) for mid-infrared narrowband emission and non-dispersive infrared (NDIR) gas sensing. By introducing rotational and non-centrosymmetric perturbations into an elliptical dimer, two high-Q resonances associated with symmetry-protected and Fabry–Pérot QBIC mechanisms are simultaneously realized within a single metasurface platform. The physical origins and electromagnetic characteristics of the two QBIC modes are elucidated through near-field field distributions, multipole decomposition, and coupled-mode analysis. The two modes exhibit distinct responses to symmetry perturbations, resulting in weak spectral coupling and separated control channels. Furthermore, the resonance wavelengths of both QBIC modes can be effectively tuned by globally scaling the dimensions of the elliptical dimer while maintaining high Q factors. By matching the FP-QBIC and SP-QBIC resonances to the characteristic absorption bands of CH₂O and NO₂, respectively, the proposed metasurface enables dual-channel NDIR gas sensing. This work provides a general strategy for designing multi-resonant high-Q metasurfaces for infrared sensing and thermal emission applications.