Observation of Periodic Perturbation Assisted Stable Bound State in the Continuum

Abstract

Bound states in the continuum (BICs) realized via metasurfaces or photonic crystals typically require strict structural periodicity. Perturbation to such periodicity are often considered detrimental, as they tend to destabilize BICs. However, controlled perturbation can hold significant applications in manipulation and offers new paradigms for high‐dimensional optical control, such as disorder‐assisted real–momentum singular points. In this work, a stable BIC that persists under periodic perturbations is theoretically and experimentally demonstrated, stabilized via edge‐state winding dependent on the layer number. Besides, by tuning the periodicity perturbation, the evolution of discrete BICs is observed from chain BICs (achieved experimentally) to the stable BIC. The findings suggest that BICs need not be strictly confined by structural periodicity, offering a new paradigm for perturbation‐induced BIC research and a flexible approach to their dynamic modulation.