Parametric study on the bimetallic cladding silica waveguide surface plasmon resonance sensor

Abstract

SPR is dedicated to the measurement of liquid refractive index. Compared with near-infrared and infrared bands, the absorption coefficient of water to visible red band is relatively low. We propose the scheme of silica on silicon and bimetallic layer, which not only reduces the light absorption of water, but also achieves higher sensing performance. In this paper, a parametric study on the bimetallic silver-gold film silica waveguide surface plasmon resonance sensor is performed by using finite element method. Red light that has a low transmission loss in water is adopted as the signal. Magnesium fluoride located between the waveguide and metal film functions as a low RI buffer layer to better couple waveguide mode and SPP mode. The effects of waveguide geometric parameters and operating wavelength on the sensing performance are investigated. Simulation results show that the buffer layer, Cr adhesion layer, operating wavelength and the Ag to Au ratio have a significant influence on surface plasmon resonance. At a bimetal thickness of Au(7nm)Ag(35nm), the sensitivity is as high as 4285 dB/RIU within the refractive index range from 1.358 to 1.365.