All-dielectric terahertz metasurfaces with high Q Fano resonance based on indirect perturbation and bound states in the continuum

Fano resonance with high Q plays an essential role in many applications. However, most Fano resonance structures with high Q based on symmetry-protected bound states in the continuum not only require high precision to control the asymmetry of the structure, but also vary significantly with the asymmetry, which is not conducive to obtaining stable and high Q Fano resonance. Here, a cuboid is added between the traditional asymmetric double parallel cuboids to obtain the asymmetric triple parallel silicon cuboids. Owing to the indirect perturbation of adding a cuboid, the proposed all-dielectric terahertz metasurfaces based on bound states in the continuum can reduce the sensitivity of asymmetry to obtain Fano resonance with high Q. Meanwhile, the proposed structure has strong robustness. Therefore, the proposed structure has numerous potential applications in nonlinear optics, filters, and biosensors.