Research On Sensing Characteristics Of Air Pollutants Based On Photonic Crystal Fiber

The structure of the photonic crystal fiber is flexible,novel and unique,which has attracted widespread attention from scholars in the application and research of sensors.Photonic crystal fiber sensors are widely used in the fields of environment,food and medicine,chemical reagents,etc.Compared with other traditional sensors,the structure is simpler,the volume is smaller,and online remote real-time detection can be performed.Photonic Crystal Fiber(PCF)sensing technology based on Surface Plasmon Resonance(SPR)has the advantages of high sensitivity of surface plasmon and flexible structure of photonic crystal fiber.Therefore,it can accurately control the evanescent field in a single-mode or multi-mode photonic crystal fiber based on the propagation characteristics of light,which is beneficial to solve the difficult problem of phase matching of the SPR structure.In summary,PCF-SPR sensor optical sensing area of development in the large space,extremely broad application prospect.Atmospheric pollutants can cause the index of refraction of photonic crystal fiber change,use of PCF-SPR sensing technology,can achieve different kinds and concentrations of measurement and remote transmission,this paper mainly revolves around PCF-SPR sensing characteristic analysis,structure design and simulation study,two different sensing structure was designed,and sensing characteristic research of using the full vector finite element method(fem),the concrete research content is as follows:This paper analyzes the basic principles of surface plasmon resonance,designs and models a photonic crystal fiber based on surface plasmon resonance,and designs a surface plasmon-based fiber with a cladding composed of four large air holes and one small air hole.Resonant photonic crystal fiber sensor.Different from the traditional multi-layer air hole polygonal arrangement structure,the sensor designed in this paper is composed of four singlelayer large air holes,which can make the coupling between the plasma film and the base film easier.Thereby it can improve the sensing sensitivity.The structure is mainly to place a metal film on the outer surface of the photonic crystal fiber,so that the sensor can directly contact the gas to be measured for detection.In this paper,the finite element simulation software COMSOL Multiphysics is used for numerical simulation,focusing on the influence of the sensor's light guide characteristics and structural parameters on the sensor performance.Through the analysis of the result value,the sensor has an average wavelength sensitivity of4050nm/RIU in the refractive index range of 1.33 to 1.40.In addition,this paper proposes a design of a higher sensitivity photonic crystal fiber sensor based on surface plasmon resonance.Based on the designed cladding layer consisting of four large air holes and one small air hole,the surface of the metal layer is coated with a layer of sensitive material.In this paper,the effects of coating graphene and black phosphorous coating on the surface of the metal layer on the sensing performance of the photonic crystal fiber sensor and the improvement effect on the sensitivity are studied respectively.Through the analysis of the result value,the sensor with this structure can reach a high sensitivity of13230nm/RIU in the refractive index range of 1.40 to 1.43.The photonic crystal fiber sensor based on surface plasmon resonance designed in this paper has the advantages of simple structure,high sensitivity and high resolution,so it has important application value in the fields of biochemistry and gas refractive index detection and sensing.