Polarization-independent quasi-BIC based on non-rotationally symmetric dimer metasurfaces

Asymmetric metasurfaces supporting quasi-bound states in the continuum (-BIC) are especially important for photonic devices because they provide high-quality factor (Q-factor) resonances. However, asymmetric metasurface structures are susceptible to the polarization state of the incident light, which limits their potential applications. In this paper, we propose a new design scheme for polarization-independent quasi-BICs without resorting to rotationally symmetric and tetramer structures. Consistent quasi-BIC resonances are observed in the metasurface consisting of asymmetric double nanorods under incident light with different polarizations. Studies of the far-field multipole decomposition and near-field distribution show that different multipoles exhibit different dependencies on the direction of polarization and that transitions between magnetic and electric quadrupoles lead to polarizationindependent quasi-BIC resonances. This work provides a new idea for designing polarization-independent high Qfactor resonators and promotes a broader range of potential applications.