Research On Surface Plasmon Resonance Sensor Based On Side-Polished Two Mode Fiber

Surface Plasmon Resonance?SPR?sensors have advantages of label-free and online real-time detection,and can be widely used in various environmental,agricultural,medical and food safety monitoring areas.Improving the sensitivity of the sensor,its simple structure,and its ability to operate in the visible and near-infrared bands are the long-standing goals of SPR research.After summarizing the research status of fiber SPR sensors at home and abroad,this paper aims to improve the performance of sensors,an SPR sensor based on the side polished two-mode fiber was proposed.Gold?Au?and Indium Tin Oxide?ITO?wwere used as thin film materials.The simulation design and optimization of the sensor,and the actual production and performance testing were studied.The specific research work of this article is summarized as follows:?1?Research on SPR sensor based on gold film-side polished two-mode fiber?SPTMF/Au-SPR?.Firstly,the finite element method was used to complete the device's simulation analysis and optimization design,The simulation results show that when the residual fiber thickness d_RFT=72?m and the Au film thickness d_Au=40nm,the maximum3705nm/RIU can be obtained within the refractive index range of 1.330-1.390RIU.Second,six SPTMF/Au-SPR sensors were fabricated and tested.Their residual fiber thickness were 69.79,71.23,72.24,69.89,71.31 and 72.34?m,respectively.The Au film thickness was 40nm.The test results show that in the refractive index range of1.333-1.404 RIU,the sensor with the d_RFT of 72.24?m has the highest sensitivity of2679.1 nm/RIU,and the full width at half maximum is 82nm,corresponding to the figure of merit 32.67RIU^-1.Compared with the same group of researchers,SPR sensors based on multi-mode fiber and single-mode fiber have significantly improved their performance:sensitivity increased by 11.95%and 36.6%,full width at half maximum decreased by 20.38%and 34.40%,respectively,and the figure of merit improved 40.64%and 108.35%.?2?Research on SPR sensor based on Indium Tin Oxide-side polished two-mode fiber?SPTMF/ITO-SPR?.Firstly,the finite element method was used to complete the device's simulation analysis and optimization design,the optimaized parameters are 72?m and 150 nm for the residual fiber thickness and ITO thickness,respectively.The average sensitivity of the LP₀₁ and LP_11a modes is as high as 10400 nm/RIU and 10150nm/RIU,respectively,in the refractive index range of 1.333-1.39 RIU.Then,six SPTMF/ITO-SPR sensors were fabricated and tested.Their residual fiber thickness were 69.23,70.19,70.87,71.34,71.96 and 72.24?m,respectively.The d_ITO was 150nm.The test results show that when the purity of the ITO target particle is 99.99%and the density is 7.1g/cm³,the test results show that in the refractive index range of 1.333-1.360 RIU,the sensor with the d_RFT of 72.24?m has the highest sensitivity of2128.76nm/RIU.The innovation of this paper:?1?The SPR sensors based on side-polished two-mode fiber,with a simple structure,a limited number of transmission modes,large effective area and mode coupling control and other advantages.?2?The SPTMF/Au-SPR sensor proposed in this paper,compared to SPR sensors based on side-polished single-mode fiber and side-polished multi-mode fiber,the sensitivity,full width at half maximum,and figure of merit are significantly improved.?3?The SPTMF/ITO-SPR sensor proposed in this paper uses ITO as a film layer material,which can effectively avoid the disadvantages of the traditional metal film being oxidized in the air,and at the same time effectively improve the sensitivity of the sensor;in addition,the resonance wavelength can be adjusted to near The infrared communication band facilitates the integration with existing communication equipment and has potential advantages in long-distance transmission and cost reduction.