Tunable Fano resonance in plasmonic MIM waveguide with P-shaped resonator for refractive index sensing

Based on the transmission characteristic of surface plasmon polaritons (SPPs), a compact plasmonic system based on a sub-wavelength metal-insulator-metal (MIM) waveguide coupled with P-shaped cavity is proposed. The results show that double Fano resonance peaks are generated in the transmission spectra, which has been studied by the finite-element method (FEM). The transmission spectrum of the system is theoretically verified by the multimode interference coupled mode theory (MICMT) perfectly. In addition, the simulation results show that the position of the resonance peaks can be adjusted by changing the structural parameters. The sensing characteristics of the resonant cavity are also studied, and the refractive index sensitivity and the figure of merit (FOM) are 2100 nm /RIU and 189.97. The results effectively improve the sensitivity and FOM of nano-scale plasmonic sensors and provide significant guidance for the application of tunable multiple Fano resonance in refractive index sensors, biosensors, optical switches and other plasmonic devices.