Theoretical Simulation Research On The Surface Plasmon Resonance Sensor And Its Application In The Measurement Of Fluid Refractive Index

As a new type of biosensor, due to the advantages of high sensitivity, good dynamic performance, no label, security and reliable, little environment affection, surface plasmon resonance(SPR) sensor is widely used in many field such as biochmistry, immunology, environment protection and medicine. Based on the analysis of principle of the surface plasmon resonance, an SPR sensor with Kretchmann configuration based on wavelength modulation technology is developed and optimized.The historical background and development tendency of the SPR sensor is introduced, and the principle of SPR sensor is analysed. The principle of the producing of Surface plasma wave(SPW) is expounded. The excitation condition of SPR is analysed, expecially on the method of Attenuated total Internal Reflection(ATR).The SPR sensor is optimized by means of Matlab simulation: Coating 2nm Cr film and 50 nm Au film on the half cylindrical prism. The optical system of SPR sensor with Kretchmann configuration based on wavelength modulation is designed and setted up to measure the refractive index of air. The experimental result show that this SPR sensor is reliable to measure the refractive index of gas. The refractive index of NaCl solution with various concentrations is measured with the SPR system. Experimental results show that resonance wavelength increases with the refractive index of NaCl solution linearly, and the sensitivity of SPR system is 5562.0nm/RIU.The method of obtaining the resonance curve by the means of dividing the reflectance of p polarized light by s polarized light in the same frequency is presented, and it is proved to be useful to promote the performance of the SPR sensor. The theoretical model of the influence of beam reshaped system and the beam diameter on the convergence angle is built. The influence of convergence angle of probe beam on resonance wavelength, the full width at half maximum(FWHM) and the depth of resonance peak is analyzed. As convergence angle decreases, resonance wavelength is enhanced, FWHM is reduced, and the depth of resonance peak is enhanced. As a result, the capacity of resisting disturbance is enhanced, and the system resolution is enhanced. It is verified that simulation result confirms the experiment data better when considering the influence of convergence angle; When the convergence angle varies from 0.8°to0°, resonance wavelength varies from 653 nm to 623 nm, FWHM is reduced from 157 nm to 117 nm, and the depth of resonance peak is enhanced from 70.5% to 93.3%.An method to promote the resolution ratio of the SPR sensor based on grating-prism structure. The promoting of the grating-prism to structure resolution ratio is simulated using Finite element method(FEM), and the simulation result shows that the resolution ratio decreased with the grating period. Comparing with the traditional SPR sensor with Kretchmann configuration based on wavelength modulation technology, when the grating period and groove depth of the gold film are 50 nm and 20 nm, the resolution ratio of SPR sensor is magnified 43.3%.