Research On Mechanism And Key Technologies Of Photonic Crystal Fiber SPR Gas Sensing

The Photonic Crystal Fiber(PCF)has been widely used in the field of gas concentration sensing due to its unique light conducting mechanism and flexible structural design,while combining with Surface Plasmon Resonance(SPR)technology to effectively improve the sensing sensitivity.Based on the design of photonic crystal fiber structure,this paper proposes a kind of PCF-SPR methane sensor filled with gassensitive materials,and then designs a kind of two-channel side-hole PCF-SPR methane and hydrogen sensor.In this paper,the PCF-SPR gas sensing mechanism is deeply analyzed,which provides a new idea for the synchronous measurement of various gas concentrations in the future.The main research content of this paper is as follows:(1)The research progress and development status of PCF gas sensing at home and abroad are reviewed.The low sensitivity and cross sensitivity of photonic crystal fiber gas sensing are discussed.The defection of gas sensing is solved by optimizing the structure of photonic crystal fiber and combining with SPR technology.(2)The novel PCF-SPR methane sensor based on gas-sensitive film was designed.A layer of metal film is plated in the air hole to stimulate the SPR effect,and a layer of gas-sensitive material whose refractive index varies linearly with the concentration of methane is coated on the inner side of the film to detect the concentration of methane.The experimental results show that the sensitivity of the methane sensor is-1.18nm/%,and the linearity is 99.98%.(3)A new PCF-SPR gas sensor with polarization filtering function was designed for simultaneous measurement of methane and hydrogen concentrations.In order to improve the spectral response of the target gas,four symmetrical super large side holes were introduced into the cladding,and two of them were coated with different composite films.The key parameters in the sensor model are optimized to realize the selective detection of specific gases.Combined with the side-hole structure and polarization filtering characteristics,the concentration of methane and hydrogen can be accurately measured without interference.The method can also be extended to the determination of certain gas concentrations in a variety of mixed gases.The final results showed that the sensitivity of methane concentration measurement can reach to-1.99nm/%,and the sensitivity of hydrogen can reach to-0.19nm/%.