In recent years, continuous bound states in the continuum (BIC) have gained significant attention for their practical applications in optics, chip technology, and modern communication. Traditional approaches to realizing and analyzing BIC typically rely on magnetic dipole models, which have limitations in quantitative analysis and integration. This creates a gap in understanding how to efficiently harness BIC with higher Q-factors for enhanced performance in real-world applications, particularly in scenarios involving terahertz imaging and multi-channel communication. In this study, we introduce a novel approach using a metallic resonator model that leverages toroidal dipole moments to generate symmetry-protected BIC with high Q-factors. By systematically varying the asymmetry parameters of the metasurface, we gradually break its symmetry, achieving a transition from the BIC mode to the quasi-BIC mode and facilitating the gradual release of stored electromagnetic energy. Our theoretical analysis confirms the existence and generation of BIC, and experimental measurements of the transmission response spectrum validate these theoretical predictions. The results indicate that terahertz metasurface with high Q-factors can produce strong resonances at specific frequencies, enhancing resistance to electromagnetic interference and ensuring stable imaging quality in complex environments. Additionally, this study suggests the potential for an integrated plasmonic ruler to achieve high-resolution and efficient biological imaging. These findings bridge the gap by demonstrating how high Q-factor BIC can be effectively utilized for multi-channel terahertz dynamic imaging and biosensing applications. This advancement lays a new foundation for developing robust systems in multi-channel communication and biomedical sensing, offering significant potential for future technological and medical innovations.

Topological photonics provides a robust framework for controlling light, with edge states offering immunity to disorder. However, utilizing this stability for practical sensing remains a challenge, as conventional high-sensitivity photonic crystal sensors suffer common imperfections. Here, we numerically design a topological photonic crystal sensor for THz refractive-index detection. The silicon-based structural slab is engineered, showing a wide photonic bandgap (PBG). By breaking the inversion symmetry, two structures with trivial and nontrivial topological phases are constructed. Due to their opposite valley Chern numbers, the topologically protected edge states can be formed at the interface. Such edge states were further integrated with the resonant cavities, so that the resonant frequencies were observed in transmittance property, forming a stable cavity–edge states coupling channel for refractive-index sensing. Numerical results demonstrate strong suppression of transmission distortion induced by boundary defects, verifying favorable topological robustness of the proposed architecture. The structure exhibits linear refractive-index response with a simulated sensitivity of 1.9 THz/RIU, outperforming conventional photonic crystal sensors in numerical comparison. This work merges topological stability of edge states with high sensitivity response of resonant frequency, offering a theoretical candidate for robust biosensing and chemical detection.