Research On Plasmon Refractive Index Sensor Based On D-shape Photonic Crystal Fiber

Surface Plasmon Reliance（SPR）sensors of photonic crystal optical fibers have great application potential in gas sensing,environmental monitoring,food safety,medical diagnosis and other fields,because they have the advantages of fast response,flexible design,high sensitivity,and no labeling.The sensitive material layer and structural parameters of photonic crystal fiber SPR sensors are two important factors affecting their sensing performance,and this paper designs different sensors from these two perspectives,and analyzes the sensing performance by using the all-vector finite element method.The main contents include:1.A structure of D-shaped photonic crystal fiber SPR sensor based on silver-aluminum oxide coating was designed.The silver layer was selected as the surface plasmon excitation material and the aluminum oxide layer was selected as the anti-oxidation protective layer.The changes of limiting loss and resonant wavelength offset of optical fiber SPR sensors under different structural parameters were analyzed,and the optimal parameter values and sensor sensitivity were studied after parameter optimization,and the final results were that the refractive index range was 1.36-1.40,the resonant wavelength of the loss spectrum was gradually redshifted,and when the refractive index was 1.40,the maximum sensitivity was 9925 nm/RIU,and the maximum resolution was 1.01×10^-4 RIU.2.In order to achieve low refractive index detection,a D-shaped photonic crystal fiber SPR sensor structure based on gold-coated groove is proposed.The influence of different gold film thickness,length and width of square groove,stomatal radius and spacing,and D-shaped polishing depth on the sensor loss spectrum was analyzed by using the full-vector finite element method,and the change law of the resonant wavelength of the loss spectrum and the sensitivity of the sensor were studied,and the structural parameters were optimized to obtain the best sensing performance.The results show that within the refractive index range of 1.25-1.29,the resonant wavelength gradually shifts to the long-wave direction,and when the refractive index is 1.29,the maximum sensitivity is 11085nm/RIU,and the maximum resolution is 9.02×10^-5RIU.3.On the basis of the second structure,a D-shaped photonic crystal fiber SPR sensor structure with gold-titanium dioxide coated groove is proposed,and a thin film titanium dioxide layer is added to the upper layer of the gold film,which enhances the protection of the gold layer and improves the sensitivity of the sensor.The influence of different structural parameters and sensitive material layers on the loss spectrum and resonant wavelength of the sensor was analyzed,and the optimal sensing performance was studied.The results show that the refractive index detection range is 1.25-1.29,and the maximum sensitivity is 24236nm/RIU and the maximum resolution is 4.13×10^-5RIU when the refractive index is 1.29.