Topologically Protected Plasmonic Bound States in the Continuum

Experimental realizations of bound states in the continuum (BICs) with strong robustness and advanced maneuverability in optical loss systems remain a long-standing challenge in nanophotonics. Here, we propose and fabricate a paradigm of diatomic metagratings incorporating the Su-Schrieffer-Heeger model into the design of plasmonic nanocavities to demonstrate optical resonators with a continuous "quasi-BICs (qBICs)-BICs-qBICs" transition. These resonators feature a topological band inversion, making high-quality (