Research On Surface Plasmon Resonance Sensor Based On Photonic Crystal Fiber

The continuous upgrading of optical fiber manufacturing technology and device performance has expanded the application fields of optical fiber sensors.And optical fiber sensor can be applied to more and more fields.The advent and prosperity of photonic crystal fiber greatly push at the research and application of optical fiber sensor.The porous structure of photonic crystal fiber(PCF)is flexible.In order to realize the surface plasmon resonance effect,it is necessary to plate a metal layer or add a metal rod on the optical fiber directly.In this paper,a new type of photonic crystal fiber is designed.The PCF cladding air holes are arranged in a normal hexagon.The effective refractive index,limiting loss,effective area of mode field,nonlinear coefficient and dispersion are simulated and analyzed by COMSOL multiphysics software.The changes of the above characteristics under different working wavelengths and different duty ratios are simulated and calculated.Through the comparison of various parameters under different structural parameters,the purpose of optimizing the structure is achieved.The structure has the characteristics of low loss and low nonlinear effect.Through comparison and optimization,it is found that when the duty cycle is 0.5,it is the most reasonable,which can not only ensure the low loss transmission of optical signal,but also realize the low nonlinear effect.When the duty cycle is 0.5,the loss is 10-11-10-9 dB/m in the range of 500nm-2000Nm,and the limiting loss increases with the increase of the working wavelength.When the duty cycle is 0.5,the nonlinear coefficient is as low as 10-5 m-1·W-1,and the nonlinear coefficient decreases with the increase of working wavelength.Secondly,a photonic crystal fiber sensor with a new structure is designed and simulated.The sensor has two detection channels,the D-shaped plane is coated with a gold layer of ml=40nm,as channel ?,which is in direct contact with the refractive index analyte.An air hole near the fiber core is selected as channel ?.A gold layer with the thickness of 40 nm is coated inside the air hole,and the center of the hole is filled with chloroform to detect the temperature.The independent detection channels enable the sensor to independently detect changes in refractive index and temperature,thereby avoiding cross-sensitivity issues.The results show that the peak loss of y-polarized light in channel ? shifts only with the change of refractive index and is not affected by temperature fluctuation.Similarly,the peak loss of x-polarized light in channel ? is sensitive to ambient temperature,but not refractive index.Finally,the influence of the thickness of the gold layer and the duty cycle on the sensitivity o are studied,and the sensor structure is optimized is further optimized to realize the independent dynamic detection of refractive index and temperature in a large range.It supports testing Refractive Index(RI)and temperature concurrently.Meanwhile it is sensitive to a large dynamic detection range,index from 1.230 to 1.355 and temperature from 5? to 85?.The results show that the sensitivities is 1645.7 nm/RIU and 803 nm/RIU when RI is in the range of 1.330 to 1.355 and the whole detectable range respectively.The sensitives when temperature is in the range of 20? to 60? and the whole detectable range is-2.68nm/? and-3nm/? respectively.The superiority of this structure is to detect SRI and temperature independently and accurately within a certain bandwidth.