Integrated plasmonic ruler using terahertz multi-BIC metasurface for digital biosensing

Abstract 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.