Topologically Protected Plasmonic Bound States in the Continuum
Shaoxin Shen, Wenxuan Liu, Jiangle He, Hui Chen, Chao Xie, Qinghao Ge, Guangxu Su, Fanxin Liu, Yasi Wang, Guoya Sun, Zhilin Yang
Abstract
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 ( Q ) resonances immune to the perturbation of incident angles and geometrical parameters. Furthermore, we strive to establish theoretical models to verify the topological nature of BICs-inspired resonances and introduce nonlinear optical probes to quantify strongly enhanced local fields at high- Q resonances. Our findings may provide a simple yet feasible design strategy for facilitating the dissipationless manipulation of surface/interface-enhanced light–matter interactions at the nanoscale, substantially broadening the functional scope of metaphotonics.