Research On Nonlinear Optical Properties And Sensing Application Of Photonic Crystal Fiber

Photonic crystal fiber(Photonic Crystal Fiber,PCF)has received extensive attention because of its flexible structural design and good optical nonlinearity.In this paper,a photonic crystal fiber and nonlinear optical characteristics are combined,and a nonlinear photonic crystal fiber methane gas sensor is designed using the four-wave mixing effect.At the same time,using the characteristic of four-wave mixing gain spectrum with two gain peaks,a nonlinear optical fiber sensor that can measure temperature and magnetic field simultaneously is proposed.This paper deeply analyzes the nonlinear PCF sensing mechanism,optimizes the sensing structure parameters,and provides ideas for designing other nonlinear PCF sensors in the future.The main research contents of the article are as follows.(1)The article summarizes the classification,characteristics,applications and development of PCF in the field of sensing,then introduces the nonlinear effects and research status of photonic crystal fibers from the perspective of nonlinear optical characteristics,and finally introduces four-wave mixing Effect and its application and development direction in PCF sensing.(2)A kind of nonlinear PCF gas sensor is designed.A sensitive film with the refractive index changing with the concentration of methane gas is coated on the air hole of the cladding.The change of the refractive index of the sensitive film will lead to the change of the nonlinear characteristics and dispersion of the fiber,which is manifested in the shift of the gain spectrum of four wave mixing.The accurate measurement of methane can be achieved by establishing the direct relationship between the peak shift of gain spectrum and the change of methane concentration.Through parameter optimization,the sensitivity of methane gas is up to-4.87nm/%.(3)A dual-parameter PCF sensor is designed based on the double gain peak generated by the four-wave mixing effect.By filling magnetic fluid in the cladding air holes,simultaneous measurement of temperature and magnetic field can be achieved,effectively solving the cross-sensitivity of temperature and magnetic field.In order to further improve the accuracy and sensitivity of the sensor,the pump wavelength is optimized.Finally,the temperature sensitivity of the sensor is-0.115nm/? and the sensitivity of the magnetic field is0.751nm/mT.The feasibility of the sensor design is verified by an example.