Practically reliable high-Q guided-mode resonances via coupler-assisted BICs

Photonic quasi-bound states in the continuum (quasi-BICs) offer a promising route to achieving high-quality (Q) factors, yet their performance is often critically sensitive to structural variations, making them vulnerable to fabrication imperfections and limiting their practical applications. Here, we address this issue by proposing a strategy based on doping additional cylindrical dielectric couplers into metasurface. By strategically repositioning two of the smaller couplers while keeping the larger ones fixed, we create a perturbation that excites a guided-mode resonance with an exceptionally high Q-factor. Consequently, the achieved Q-factor is three orders of magnitude higher than that obtained through conventional symmetry-perturbation methods. Our design provides an effective solution to the severe performance degradation caused by fabrication defects in traditional symmetry-breaking metasurfaces, establishing a new pathway toward practically reliable high-Q resonances that are resilient to manufacturing tolerances in both classical and quantum photonic platforms.