Design And Research Of SPR Sensor For High-sensitivity Photonic Crystal Fiber

Surface Plasmon Resonance（SPR）sensors are highly sensitive to changes in the refractive index（RI）of external samples and have the advantages of high sensitivity and real-time detection.However,traditional SPR sensors are bulky,which limits their practical application.Photonic crystal fiber（PCF）SPR sensors not only overcome this disadvantage but also have the advantages of high sensitivity and remote detection.They show great advantages in fields such as biochemical sensing,environmental monitoring,and bacteria identification.To improve their sensing performance,this article is based on the sensing principle of SPR and existing research results at home and abroad.It proposes D-type single-side polished,double-side polished PCF-SPR sensors,and eccentric core PCF-SPR sensors.Finite element methods are used to study the performance of the sensors.The main research content of this article is as follows:1.Using the D-type double-side polished PCF-SPR sensor as the model structure,the influence of two plasmonic materials（Au,Ag）and Ti O₂ on the sensor’s performance is investigated.The results show that the sensor using Au as the sensitive layer has higher sensitivity.Furthermore,the sensor coated with Ti O₂ has higher sensitivity than the one without Ti O₂,providing a basis for subsequent design work.2.A D-type single sided polished PCF-SPR sensor is proposed,which grinds and polishes one side of the optical fiber.Coating Au-Ti O₂ composite film on the polished surface as a plasma material,with a detection channel on the outer side for convenient detection.A sensor that models and simulates its structure through COMSOL Multiphysics,and optimizes its structural parameters to achieve optimal performance.The results indicate that the detection range of the sensor is1.35-1.4.When the refractive index of the external sample analyte is 1.4,the wavelength sensitivity reaches a maximum of 20,102 nm/RIU.This sensor is an external sensor,which not only has high sensitivity but also is relatively simple to manufacture and detect.3.The single-side polished PCF-SPR sensor is improved,and a D-type double-side polished PCF-SPR sensor is proposed.Both sides of the sensor are polished,and an Au-Ti O₂ composite film is attached to the polished surface as the sensitive layer.The results show that the double-sided polishing design enables the sensor to have higher sensitivity,and the wavelength sensitivity of the sensor can reach 22,100 nm/RIU when the refractive index of the external sample analyte is 1.42.In addition,the sensor is also applied to detect methane concentration,and simulation results show that the average gas sensitivity of the sensor can reach 11 nm/%.4.A type of eccentric core PCF-SPR sensor has been proposed,which shortens the distance between the fiber core center and the metal film,and enhances the coupling between the fiber core mode and the surface plasmon polariton（SPP）mode.The results show that the eccentric design improves the performance of the sensor.When the refractive index of the external sample analyte is1.4,the wavelength sensitivity of the sensor reaches a maximum of 20,360 nm/RIU,and the detection range of the sensor is 1.33-1.4.The sensor was also used to detect pathogens in water,and the simulation results show that the wavelength sensitivities of the sensor to Vibrio cholerae,Escherichia coli,Bacillus anthracis,and Enterococcus were 2,685 nm/RIU,4,409 nm/RIU,3,344nm/RIU,and 4,524 nm/RIU,respectively.Compared with the D-type double-side polished PCF-SPR sensor proposed above,the eccentric core PCF-SPR sensor has higher sensitivity and wider detection range,and can be widely used in gas detection,biosensing,and other fields.