Dual-band terahertz metasurface biosensor based on electromagnetically induced transparency effects for antibiotic detection

This study presents a dual-band terahertz metasurface biosensor based on the electromagnetically induced transparency (EIT) effect. The sensor employs copper resonant rings and a quartz dielectric substrate, enabling switching between single and dual-EIT (D-EIT) modes by altering the polarization direction of incident terahertz waves. The physical mechanism of the dual-EIT effect was elucidated through electric field analysis, revealing bright-dark mode coupling (0.53 THz) and bright-bright mode coupling (0.76 THz). Simulations demonstrated a refractive index sensitivity of up to 220 GHz/RIU. Experimentally, the metasurfacel fabricated via laser engraving exhibited dual-frequency sensing capabilities for lactose and chlortetracycline hydrochloride, with a minimum detectable concentration of 0.1 mg/L in both aqueous and milk solutions. Despite limitations in low-concentration detection within complex media due to increased optical loss, this sensor shows significant potential for applications in food safety and antibiotic residue monitoring.