Study On SPR Sensing Characteristics Of Photonic Crystal Fiber Coated With Functional Material

As a new type of sensing platform,photonic crystal fiber(PCF)has received extensive attention from researchers at home and abroad for its excellent light control characteristics and flexible structural design.PCF sensing structures based on different sensing principles have been proposed one after another.Among them,the PCF-SPR sensor based on Surface Plasmon Resonance(SPR)technology has the unique advantages of strong stability,high sensitivity and strong expansibility,and has become one of the important researches and development directions in various sensor fields,which has shown great application value in the fields of biomedical testing and safety monitoring.The external sensing type PCF-SPR structure has a good application prospect because its sensing channel is located outside the PCF cladding,which objectively reduces the process difficulty of coating.At present,the external sensing PCF-SPR is mostly used for the detection of a single refractive index parameter,and due to the poor tunability of the SPR limiting loss peak,the simultaneous detection of multiple parameters cannot be achieved.Therefore,based on the starting point of expanding the application of external sensing PCF-SPR,this article mainly completes the following tasks:(1)Investigate the application development and study status of photonic crystal fiber(PCF)in sensing,focusing on the study status of PCF-SPR sensing based on functional material coating.Introduce the coupled mode theory and the basic principles of SPR technology,and explain the numerical calculation and analysis methods.(2)An external sensing PCF-SPR temperature sensor based on functional material coating is proposed.By plating a gold nano-film on the outer side of the PCF cladding layer containing only a single layer of air holes,compared with the coating structure of the inner wall of the cladding air hole,the process difficulty is reduced.Introduce polydimethylsiloxane(PDMS),a temperature-sensitive material with negative thermooptical coefficient,good biocompatibility and non-volatile.In addition,the temperature-sensitive material directly contacts the environment to be measured,and can quickly sense the temperature of the environment to be measured and realize rapid detection.Numerical calculation results show that the temperature sensitivity and resolution are-8.18nm/°C and 0.0123°C,respectively,while maintaining good linearity.Expanded the application of external sensing PCF-SPR in the field of temperature measurement.(3)Based on the research of D-type and grooved PCF-SPR sensors and combined with the temperature sensor designed above,a SPR temperature and refractive index sensor based on Symmetrical Side Polished(SSP)photonic crystal fiber is proposed.A symmetrical polishing surface similar to the D-shaped structure is introduced on the PCF.One polishing surface is only coated with gold nano-film as the refractive index sensing channel,and the other side is coated with gold nano-film and PDMS temperature-sensitive film,respectively.Two sensing channels are formed,and the finite element method(FEM)is used to perform numerical calculation and analysis on the transmission and sensing characteristics of the proposed structure.The results show that the dual sensing channels are independent of each other,which solves the crosssensitivity problem of multi-parameter sensors from the source.The refractive index and temperature sensitivity are and respectively,which can realize the simultaneous measurement of refractive index and temperature.