Research On The Near-infrared Spectrum Of Spr Sensors Based On Microstructured Optic Fiber For Low Ris Detection

With the development of SPR sensors based on microstructured optic fiber（MOF）,a large number of sensing models have been proposed and analyzed.In this paper,the designs are mainly used for detecting low RIs materials including halogenated ether,fluorine-containing organics,medical oxygen,liquid CO₂,aerogel,sevoflurane and so on.According to the principle of SPR excitation and the sensing mechanism of MOF-SPR,three structural models have been designed and investigated based on COMSOL Multiphysics software via the finite element method（FEM）.Numerical simulations reveal that the spectral characteristics and sensing performances of these sensors in the near infrared region.The novel SPR sensor based on microstructured optic fiber with dual（big）open rings is presented,which can detect the near infrared region from 1470 nm to 2150 nm for RIs of 1.22-1.36.The analysis of spectrum shows a maximum wavelength sensitivity of 12400 nm/RIU and corresponding resolution of 8.06×10^-6 RIU can be observed.Besides,the Ag-Au dual layers are selected as the plasmonic materials and the silver layer is covered by a gold layer for protection against oxidation.The novel SPR sensor based on D-shaped microstructured optic fiber with ITO coatings has been proposed,which can detect analyte RIs from 1.22 to 1.33 in the near infrared wavelength of 1450 nm-2010 nm.The maximum spectral sensitivity of 15000 nm/RIU and the maximum amplitude sensitivity of 442.47 RIU^-1 are validated with a high resolution of6.67×10^-6RIU.And indium tin oxide（ITO）is a better conductor for initiating surface plasmon resonance in the near infrared range.The novel SPR sensor based on series-wound microstructured optic fiber with dual gold nanowires is investigated and analyzed,which possesses a broad range of detection for low RIs changing from 1.13 to 1.35 with the near infrared region of 865 nm-1765 nm.A high spectral sensitivity of 17500 nm/RIU and amplitude sensitivity of 296.54 RIU^-1 are obtained,and the optimal resolution is up to 5.71×10^-6 RIU.The coupling effect can be generated by dual cores due to the symmetrical structure of proposed sensor,which optimizes the sensing performances.Furthermore,compared to the traditional coating method,this nanowire structure simplifies the fabrication process for this sensor.