Exploration of enhanced stabilized-multibound-state-assisted optical response in symmetric dielectric metasurfaces

Bound states in the continuum (BICs) exhibit enormous potential for advancing optical response due to their ultra-high Q factors. However, their practical applications are hindered by scattering losses caused by fabrication defects. This study proposes a strategy of merging multiple bound states at the Γ point of symmetric dielectric metasurfaces, aiming to enhance their optical response performance. Based on photonic crystal slabs with C4v/C6v symmetry, we designed structures that support symmetry-protected BICs and multiple accidental BICs capable of merging and separating. The Q factor of the C4v structure at the high-symmetry point remains consistently at 108. Then we can enhance the Q factor of the C6v structure up to 1010 by merging multiple accidental BICs. The merged states maintain excellent stability against variations in the lattice period, which significantly improves the optical responses. We experimentally achieved precise determination of the Q factor, and these results are in excellent agreement with the simulation data. This study of merged BICs provides a novel approach for the development of high-performance sensing and high-precision detection technologies.