Optical Sensing Research Based On Polarized-dependent Absorption Of Graphene

Graphene is a flat monolayer of carbon atoms arranged in two dimensional honeycomb lattice,which has attracted extensive attention among scientific community and become the hotspot and front of researches in many disciplines,due to its unique properties arisen from the unique structure.In recent years,graphene is theoretically and experimentally found to show more absorption for s-polarized wave than p-polarized wave under total internal reflection(TIR).The polarized-dependent absorption property of graphene has been utilized in various fields,such as accurate determination of number of graphene layers,3D topography plotting of graphene,graphene information storage,refractive index(RI)sensing and cancer cell flow cytometry.In this dissertation,the prism and fiber optic sensing models based on graphene polarized-dependent absorption is designed and analyzed in theory.This work was funded by National Natural Science Foundation of China(Grant No.61575150)and the main research results are as follows:1.Prism sensing model based on GPDA was built and the mechanism of GPDA was analyzed through MATLAB and COMSOL Multiphysics respectively.It was found that the reflectance decrease is caused by the joule loss due to the incident light-induced current in graphene,and the reflectance difference?R between s-and p-polarized wave is sensitive to the RI change of environment,which can be described by y=-364.061+811.331x-603.41x~2+149.848x~3.Smaller RI of prism and more graphene layers result in higher sensitivity;2.Multilayer-graphene(regarded as graphite)was found to be able to totally absorb s-or p-polarized wave from 300-590 nm as long as the number of graphite layers and the incident angle are set appropriately;3.Fiber optic sensing model based on GPDA was built and parameters were optimized as follows:number of graphite layers N=55,diameter of the core D=600?m,sensing region length L=4 mm,numerical aperture NA=0.24,with which the fiber optic sensor has a sensing curve of y=-51991.95+1174300x-884285.71x~2+222222.222x~3(R~2=0.99992)with average sensitivity of 2300 nm/RIU;4.Reflection spectra of fiber Bragg grating were studied using MATLAB and COMSOL with different calculating methods.Reflection spectra calculated by coupled mode method and multilayer matrix method matched well,while that by COMSOL Multiphysics showed center wavelength shifts;5 Optical deposition of graphene oxide(GO)and its influence factors including poly(methyl methacrylate)(PMMA)adding,light intensity,light mode and deposition time were investigated,and the saturated absorption property of optically deposited GO was tested.