A Symmetric MIM Waveguide Structure of a High-Sensitivity Refractive Index Sensor

Here in, a high sensitivity nano-sensor structure consisting of a metal-insulator-metal (MIM) wave-guide with a baffle coupled with a bearing circular ring cavity (BCRC) is designed based on surface plasmon polaritons. The propagation characteristics of the plasmonic wave-guide coupled system is analyzed by using finite element analysis (FEA). The sharp asymmetric Fano resonance in the transmission spectrum is generated by the interaction between continuous wideband resonance of the baffle on the wave-guide and discrete narrowband resonance of the BCRC, which is demonstrated by simulation results. At the same time, the influence of different parameters on the performance of the structure is analyzed. The maximum sensitivity of the refractive-index sensor is 3220 nm/RIU with a high FOM of 57.5. The investigation of the designed structure breaks through the restrictions of some traditional cavities and provides a cavity choice for designing nano-photon sensors based on surface plasmons.