Topologically Protected Plasmonic Bound States in the Continuum

• Published in: Nano letters 2024-10, Vol.24 (42), p.13285-13292
• Main Authors: Shen, Shaoxin, Liu, Wenxuan, He, Jiangle, Chen, Hui, Xie, Chao, Ge, Qinghao, Su, Guangxu, Liu, Fanxin, Wang, Yasi, Sun, Guoya, Yang, Zhilin
• Format: Article
• Language: English
• ISSN: 1530-6984; 1530-6992; 1530-6992
• DOI: 10.1021/acs.nanolett.4c03636

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.