Numerical study on the biosensing in mid-infrared based on multiple Fano-resonance plasmonic waveguide

Abstract

In this article, the metal-insulator-metal based Fano resonance biosensors in mid-infrared are numerically investigated. The continuum states and discrete states of Fano resonances are produced by two asymmetric stubs and a symmetric ring, respectively. The quadruple Fano modes can be individually modulated for refractive index sensing in the mid-infrared spectral region (3–10 µm), which covering the characteristic infrared vibrations of specific molecular species. The maximum sensitivity and figure of merit is up to 7550 nm/RIU and 302, respectively. Moreover, the temperature sensing in ethanol and the concentration sensing in glucose solution indicate that the waveguide can not only quantify the temperature and concentration of the solution through the Fano resonance, but also characterize the chemical information of sample through the mid-infrared absorption. And the optimized MIM waveguide can effectively prevent the absorption of the aqueous solution disturbs the transmission spectrum and enhance the mid-infrared absorption of solvents. The excellent performances demonstrate the tunable multiple Fano resonance based on MIM waveguide is a promising method for biosensing in mid-infrared.