Dynamically tunable multiple quasi-bound states in the continuum based on the phase-change metasurface

Bound states in the continuum (BICs) have garnered significant attention in recent years due to their ability to enhance light–matter interaction. The high quality ( Q ) factors of quasi-BICs make them particularly promising for applications such as lasing, sensing, and nonlinear harmonic enhancement. Here, we numerically and experimentally demonstrate dynamically tunable multiple quasi-BICs by integrating aluminum rod arrays with GST. By tailoring the geometric parameters of the aluminum rod arrays, multiple quasi-BICs are achieved, manifesting as distinct Fano resonances in the terahertz transmission spectrum. Upon coating the aluminum rod arrays with GST, both the resonant frequencies and linewidths of the quasi-BICs can be dynamically tuned through the phase transition of GST from the amorphous to the crystalline phase. Furthermore, these quasi-BICs exhibit strong electromagnetic field confinement, which can be significantly modulated via the GST phase transition. The dynamically tunable multiple quasi-BICs offer promising potential for applications in terahertz modulators, filters, and imaging.