Plasmonic Sensor Based on S-Shaped Metal-Insulator-Metal Waveguide for the Detection of Water-Soluble Vitamins

In this study, a compact plasmonic sensor that can generate dual Fano resonances is proposed. The structure is composed of a metal-insulator-metal (MIM) S-shaped waveguide with baffle, an analogous C-shaped resonator (ACR), and a T-shaped resonator with an annular cavity (TRAC). Employing the finite element method (FEM), the optical transmission characteristics of the structure are investigated. The results indicate that the dual Fano resonances arise from different resonators and can be independently tuned by altering the structural parameters of different resonators. Then, through adjusting the refractive index (RI) of the medium within the resonator in the range of 1.3–1.4, the RI sensing properties of the structure are also analyzed. The maximum RI sensitivity (S) and figure of merit (FOM) can be up to 2400 nm/RIU and 95.86 RIU⁻¹. Moreover, depending on the independence of the ACR and the TRAC, the sensor has efficient biochemical sensing characteristics and is used to achieve simultaneous determination of water-soluble vitamin B1 and vitamin C. The corresponding concentration sensitivities can be up to 500 nm·ml/g and 224 nm/C_vc, respectively. Consequently, the structure has significant potential for multifunctional biochemical sensing applications in high-density integrated circuits.