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

Abstract

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 the 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.