Lattice‐Enhanced Fano Resonances from Bound States in the Continuum Metasurfaces

Abstract Fano resonances in metamaterials are known for their high quality ( Q ) factor and high sensitivity to external perturbations, which makes them attractive for sensors, lasers, and nonlinear and slow light devices. However, Fano resonances with higher Q factors obtained through structural optimization of individual resonators are accompanied by lower resonance intensity, thereby limiting the overall figure of merit ( FoM ) of the resonance. Here, a strategy for simultaneously enhancing the Q factor and FoM of Fano resonances in terahertz metamaterials is reported. Coupling of the Fano resonance, which arises from a symmetry‐protected bound state in continuum, to the first‐order lattice mode of the metamaterial array leads to stronger field confinement and substantial enhancement of both Q factor and FoM . As such enhancement occurs in planar metamaterials independently of the resonator geometry, the proposed approach can be utilized for a wide range of high‐ Q and high‐sensitivity terahertz metadevices.