Tunable Nano Refractive-Index Sensor Structure Base on Fano Resonance

Here in, a tunable nano refractive index sensor structure consisting of a metal-insulator-metal (MIM) waveguide with a metal stub coupled with a protractor type half ring cavity (PTHRC) is designed based on surface plasmon polaritons. The propagation characteristics of the plasmonic waveguide coupled system is analyzed by using finite element method (FEM). The sharp asymmetric Fano resonance in the transmission spectrum is generated by the interaction between narrow discrete mode of the PTHRC and wide continuous mode of the metal stub on the waveguide, which is demonstrated by simulation results. At the same time, the influence of diverse arguments on the performance of the nano-sensor system is analyzed, and the shape and position of the formant can be adjusted by changing the key arguments. The maximum sensitivity and FOM of the refractive-index sensor is 1600 nm/RIU and 50. The investigation has potential application prospect in optical integrated circuit and it also provides a tunable and easy to fabricate structure choice for nano-biosensors and other fields.