Optimization of tunable symmetric SPR sensor based on Ag-graphene

Abstract

To overcome the limitations of low sensitivity and instability of metal-medium-metal tunable surface plasmon resonance (SPR) sensors excited by planar waveguides, a silver-graphene-medium-graphene-silver film symmetrical SPR sensing structure excited by planar waveguides is proposed. And optimize sensor performance through modeling. The principle of symmetry structure for sensing tunability is analysed, finding that sensing with a silver film has a higher sensitivity than a gold film. However, since the silver film is easily oxidized, it affects the stability and repeatability of the sensor. To solve this problem, the graphene layer is added to the silver film to improve the disadvantage of easy oxidation of the silver film. A plane waveguide with a refractive index distribution of the residual error function of the excitation is prepared by ion exchange. The sensor structure was modeled and analyzed, and the influence of metal material, metal thickness, graphene layer number and thickness of the detection medium on the performance of the sensor was studied, and the sensing structure was better optimized. The results show that the silver film has a better sensing performance and higher sensitivity than the gold film. By adjusting the thickness of the detection medium, the refractive index range of the detection medium has a certain tunability: the choice of graphene thickness optimises sensor stability and detection sensitivity.