Research Of Multi-layer Fiber-optic Surface Plasmon Resonance Sensor Based On Enhanced Sensitivity

Optical fiber surface plasmon resonance（SPR）sensors are rapidly becoming key devices in the fields of biological detection,environmental monitoring,and food safety due to their superior performance of anti-electromagnetic interference,label-free,and so on.Sensitivity enhancement is the key to improving sensor performance and realizing instrumentation.Based on the current research status of optical fiber SPR sensors,this dissertation considers the materials and the structures of the sensor,using the excellent photoelectric properties of nanomaterials,building the simulation model,and preparing sensors with different structures,so as to improve the sensor performance.On the basis,the main work of this dissertation is indicated as below:1.The theoretical basis for optical fiber SPR sensing is provided by building multiple simulation models.The cross-section model of the sensor is established by the finite element method to study the electric field distribution on the surface of the sensor.The simulation model of nanomaterials is built using the first principles,and the dispersion relationship of nanomaterials is calculated.The resonance spectrum of the sensor is simulated by the transfer matrix method to study the change of resonance wavelength.2.The influence of sensor materials on sensitivity is studied.By combining the multi-objective optimization genetic algorithm and the transfer matrix method,the sensor sensitivity and the full width at half maximum are studied to achieve the optimal configuration of the thicknesses of multi-layer materials.The results show that the sensitivity range of most configurations is 3411.426 nm/RIU-5948.048 nm/RIU and the quality factor range is 66.711 RIU^-1-157.570 RIU^-1.And a sensor configuration with good performance can be selected according to actual needs.3.The influence of tapered fiber structure on sensitivity is studied.The sensitization effect of tapered fiber is studied through simulation and experiment.The simulation results show that as the taper ratio increases,the sensitivity of the sensor also increases.However,the experimental results show that the increase of the taper ratio will cause the sensitivity of the sensor to first increase and then decrease.The sensitivity of the sensor with the taper ratio of 2 is 15.49%higher than that of the conventional multimode fiber sensor.The results show that the tapered fiber structure has a certain sensitivity enhancement.The reason why the simulation results are different from the experimental results is analyzed.4.The influence of the coating structure of WS₂ on the sensitivity is studied.A novel SPR sensor with the structure of tapered fiber WS₂-Au is successfully prepared.The influence of the thickness of the WS₂ nanosheet on the sensitivity of the sensor is studied through simulation and experiment.The increase of the thickness of WS₂nanosheet makes the sensor sensitivity first increase and then decrease.The experimental comparison of the tapered fiber WS₂-Au SPR sensor and the tapered fiber Au-WS₂ SPR sensor are carried out.It can be concluded that the experimental refractive index sensitivity of the tapered fiber WS₂-Au SPR sensor can reach 4158.171 nm/RIU,which is 125.83%higher than that of the conventional multimode fiber SPR sensor,and50.12%higher than that of the tapered fiber Au-WS₂ SPR sensor,showing good sensitivity enhancement effect.Finally,a biosensor is built to detect prostate specific antigen,and the feasibility of the sensor in the field of biodetection is studied.