Graphene-assisted electromagnetically induced transparency-like terahertz bio-sensor for ultrasensitive detection using optics-enhanced sensing

In recent years, biosensors based on terahertz metamaterials have emerged as a prominent area of research. However, studies focusing on enhancing biosensing performance through optical pumping to improve sensitivity are scarce. This paper proposes a graphene-based electromagnetically induced transparency-like (EIT-like) optics-enhanced terahertz metamaterials biosensor. Using this biosensing platform, we successfully detected glycine through amplitude modulation, achieving a limit of detection (LOD) of 1 pg/mL. Additionally, we developed an optics-enhanced sensing method where the conductivity of graphene is reduced, resulting in a significant increase in the amplitude of the device's transmission spectrum as optics-enhanced. Experimental results demonstrate that the change in the transmission amplitude at varying concentrations exhibits a quasi-linear relationship as the optical-energy-density is varied from 0 µJ/cm² to 119.7 µJ/cm². For a low concentration of glycine (32 pg/mL), the optics-enhanced sensing peak amplitude rate of change (<i>AR</i>) reached a maximum of 857.5% at an optical-energy-density of 119.7 µJ/cm². Furthermore, the graphene-based terahertz metasurfaces biosensor (Gra + Ms) successfully detected a glycine concentration of 1 pg/mL, which would have been undetectable in the absence of optics. These findings suggest that the sensitivity of the Gra + Ms sensor is significantly enhanced under the optical pumping, allowing for more precise detection of low glycine concentrations. This study offers a promising new direction for the practical application of terahertz metamaterials in biosensing.