Design And Research Of Terminal Reflective Fiber Optic SPR Sensor

Surface Plasmon Resonance（SPR）is a phenomenon based on the interaction of electromagnetic waves with surface plasma.Since the SPR phenomenon is highly sensitive to the refractive index of the medium,SPR technology can achieve high-sensitivity detection,which makes SPR sensors have great advantages in the detection of substances.In order to improve the performance of optical fiber SPR sensors,this paper proposes terminal reflective fiber SPR sensors with different structures,combined with the further optimization and adjustment of sensitive layer materials and fiber structures,and uses the full-vector finite element method to simulate and calculate,and their light field distribution is studied.Through simulation analysis,the sensor performance data under different environmental refractive indices is obtained,and they are comprehensively evaluated.The results of this study can provide strong theoretical support for the selection and optimization of sensors in practical applications.The main work of this study includes:（1）In order to improve the sensitivity of optical fiber SPR sensors,this paper designs Cr/Au/Ti O₂ composite film as a sensitive layer on the basis of traditional single-layer metal film,combines the optimization and adjustment of sensitive layer materials and optical fiber structure,and uses the full-vector finite element method to simulate and calculate,and analyzes the influence of different parameters on sensing performance.Through the construction of model structure and the study of material properties,the dependence of model sensing characteristics on geometric structure parameters is analyzed,and the influence of different structural parameters on the reflection spectrum is discussed.Based on the wavelength modulation method,the feasibility of refractive index detection is proved.This sensing model provides a theoretical basis and research method for cladding SPR sensors in the next chapter.（2）In order to reduce the practical difficulty of coating on the surface of the fiber core,a fiber optic grooved cladding SPR sensor is proposed.While the structure of the optical fiber changes,the purpose of leaking and coupling the transmitted light in the fiber core to the optical fiber cladding is achieved,so that the SPR effect occurs when the evictile field is in contact with the metal film on the surface of the cladding.Rsoft software is used to model the fiber structure of the groove structure and study the light field distribution,and the results show that changing the fiber structure can indeed verify the cladding mode by changing the fiber structure.Secondly,the groove depth is optimized to obtain the optimal structure to obtain the average wavelength sensitivity and maximum sensitivity of the sensor in the refractive index detection range.This structure provides a basis for further analysis of periodic groove structures in the next chapter.（3）In order to verify the influence of the number of grooves and spacing on the performance of the sensor,a periodic optical fiber groove cladding SPR sensor is designed,the number of grooves is increased to multiple with a certain spacing to form a periodic structure,and the optical fiber structure of the periodic groove is modeled and the optical field distribution is studied by Rsoft software to verify the influence of structural changes on core energy transmission,and the parameters of the periodic structure（number of grooves,cycle length）are optimized to obtain the optimal structure,and the optimized sensors are compared.The results show that the periodic groove structure has higher wavelength sensitivity than other cladding SPR sensors.This sensing model reduces the cumbersome steps of stripping the cladding and then coating the multilayer film,and SPR detection can be completed by directly coating the metal film on the cladding layer,which is of great significance for optical fiber cladding SPR sensors.