Realization of robust high-Q resonances of BICsvia eigenfield perturbations in a multiple-notched nanocube metasurface

Non-radiative bound states in the continuum (BICs) allow the construction of resonances with high-quality (Q) factors and have emerged as an attractive platform for manipulating light-matter interactions on the nanoscale. However, current studies on symmetry-protected BICs (SP-BICs) suffer from a fundamental trade-off between the Q factor and asymmetric parameters, presenting a significant hurdle for practical applications. Here, utilizing the eigenfield perturbations, we successfully break the conventional inverse quadratic law of the SP-BICs and realize the robust high-Q resonances against the asymmetric parameters. We find the introductions of the central notch can efficiently boost the resonance of the electric quadrupole, which results in the enhancement of multiple-mode interference, and thus improving Q factors, while the constant effective refractive index guarantees the resonance with a stable wavelength. Our findings provide a promising strategy for modulating the light-matter interaction and may pave the way for applications in future high-performance optoelectronic devices.