Controllable conversion between symmetry-protected and accidental bound states in the continuum via lattice hybridization

Bound states in the continuum (BICs) in periodic nanophotonic structures provide a powerful route to achieving ultrahigh- Q resonances and strong light–matter interactions. However, controllable interconversion between different classes of BICs remains challenging. Here, we propose and experimentally demonstrate a dual-lattice metasurface platform that enables the systematic conversion between symmetry-protected BICs and accidental BICs through lattice hybridization and dipolar interference. By introducing two square lattices with either a relative in-plane displacement or a controlled size detuning of the central elements, we reveal two independent yet physically equivalent pathways to tailor the interference between electric and magnetic dipolar resonances. This interference leads to the emergence of accidental BICs without requiring intricate geometric optimization, and further gives rise to electromagnetically induced transparency-like spectral features during the BIC transition. Experimental measurements show excellent agreement with numerical simulations. Our results provide clear physical insight into the origin of accidental BICs in hybridized lattices and establish a versatile strategy for engineering high- Q resonances in metasurfaces with potentials for diverse applications.