Study of the Surface Plasmon Refractive Index Nanosensor Based on Fanoresonance

Abstract

In order to solve the problems of low sensitivity and complex structure of surface –plasmon- polariton (SPP) sensor at the present stage, a highly sensitive and stable SPP sensor composed of metal-insulator-metal (MIM) waveguide, a stub and a resonant cavity is proposed. The diameter of the MIM waveguide is chosen to be 50 nm so that only the single mode exists. The radius and refractive index of the cavity can vary, which is imbedded in silver background so that SPP phenomenon can be produced. The optical transmission characteristics and sensing characteristics of the designed sensor are studied by using finite element method. Experimental results show that the combination of the MIM waveguide and the stub can produce continuous state and the cavity can produce discrete state at the wavelength of 830 nm. At the same time, our research also demonstrates the sharp asymmetric Fano transmission spectrum is also sensitive to the surrounding medium. The application of the designed device in the field of refractive index sensing is also studied by calculating the shift of the resonant wavelength with the change of the refractive index of the medium in the resonator. The device can achieve refractive index sensing performance with the sensitivity of 803 nm/RIU and the figure of merit of 121.