Design And Simulation Of Taper Optical Fiber SPR Sensor Based On Hyperbolic Metamaterials

Surface Plasmon Resonance(SPR)acts as a surface analysis technique.There are existing applications in different fields: such as biosensing,medical health,environmental monitoring and other fields,ascribing to the advantages of high resolution,fast response,and high sensitivity.However,the improvement in sensitivity is very limited due to typical materials(such as: Au,Ag,Al,etc.)themselves have a small dispersion modification.Hyperbolic metamaterials(HMMs)have attracted extensive attention of researchers ascribing to flexibly adjust their dispersion by controlling material parameters,and have been applied to side-polished optical fiber to form a new SPR sensor(HMMs-SPR).But its preparation process is complicated and it is difficult to ensure the flatness of the polished aera.Therefore,in this paper,a HMMs-SPR sensor based on a tapered fiber is proposed,which has a simple preparation method and can provide a stronger evanescent field effect to obtain higher sensing sensitivity.Based on above work,polydimethylsiloxane(PDMS),as a temperature-sensitive material,is coating on the HMMs to form a temperature sensor.It can further expand its application range.The specific research contents are as follows:(1)The influencing factors of refractive index and temperature performance of SPR sensor based on HMMs are preliminarily analyzed by using effective medium theory(EMT).Firstly,the equivalent dielectric constant of HMMs with different composition materials and metal filling rate is obtained by EMT.After it is brought into the phase matching condition,the corresponding resonant wavelength and theoretical sensitivity of the sensor can be obtained.Taking the sensing sensitivity as the evaluation standard,the influence and better solution of the two parameters are preliminarily determined,and compared with the SPR performance based on Au and Ag film.(2)The structural parameters of HMMs-SPR sensor are optimized by using finite element software COMSOL Multiphysics,taking the transmission spectrum of fundamental mode as research object.The SPR structure sensitivity and spectral comprehensive figure of merit were evaluated in terms of material composition,metal filling rate,number of bilayers,bilayer thickness,and diameter of the taper fiber of the HMMs.After obtaining the optimal parameter conditions,the comprehensive response characteristics of the sensor in the refractive index range of 1.33 RIU to 1.40 RIU were simulated and compared with the SPR performance based on Ag film.(3)Based on the HMMs-SPR structure in the above chapter 3 and 4,a layer of temperature-sensitive material(PDMS)is coated on the HMMs acts as temperature sensor.The same research object and evaluation criteria is also used to study the effects of the material composition of HMMs,PDMS thickness under different metal filling ratios and the diameter of the tapered coreless fiber on the temperature sensing performance of the SPR structure.After obtaining the optimal parameters,comprehensive response characteristics of the sensor in the range of from 20 ℃ to 70 ℃is simulated and compared with the SPR structure based on the Ag film.