A novel method to improve the measurement accuracy of multilayer surface plasmon resonance sensor

In this paper, a novel method to improve the measurement accuracy of multilayer surface plasmon resonance (SPR) sensor is proposed. Based on the Kretschmann SPR sensor, the measurement layer is transferred from the outermost layer to the inside of the structure (in the form of prism-metal-measurement-dielectric layer), the new structure shows excellent linear relationship between the refractive index (RI) and the resonance wavelength with the linear fitting coefficient improved from 0.97048 to 0.99904, and the measurement error reduced by 96.75 %, which can greatly improves the measurement accuracy. In the simulation of the five-layer, six-layer and seven-layer structure, it is verified that the conclusion of four-layer structure is also applicable to multilayer structures, the detailed analysis and explanation are also discussed. As an example, magnetic fluid (MF) film is selected as the measurement layer to demonstrate the performance of the designed structure. Parameters of the structure were optimized by simulation, the optimal thickness of the MF layer is 120 nm and the optimal RI of dielectric layer is 1.35. With these optimized parameters, the measurement accuracy is greatly improved and the measurement sensitivity of magnetic field is 5nm/mT. The idea is also expected to be applied to other types of SPR sensors to achieve higher measurement accuracy.