Nonlinear Optical Properties Of Composite Films Based On Two-dimensional Material Black Phosphorus

In order to improve the nonlinear optical(NLO)properties of semiconductor black phosphorus(BP)and broaden its applications in the nonlinear optical field.In this thesis,BP nanosheets were prepared by liquid phase stripping method,and then Al₂O₃/BP/Ag composite films,Al₂O₃/BP/PMMA/Ag composite films and Al₂O₃/BP/Al₂O₃/Ag composite films were prepared by spin coating method and magnetron sputtering method.The morphology,structure and crystal quality of the samples were analyzed by scanning electron microscopy(SEM)and transmission electron microscopy(TEM).The linear and nonlinear optical properties of the samples were tested and analyzed by UV-Vis spectrophotometer(UV-Vis)and femtosecond Z-scanning technology.The nonlinear absorption(NLA)characteristics of the samples were improved by the surface plasmonon(SP)effect of Ag nanoparticles(Ag NPs)and the change of polarization medium.The effects of different sputtering power of Ag NPs,different content of BP nanoparticles and the change of laser energy density on the third-order nonlinear absorption characteristics were investigated.The main research results are as follows:(1)The transformation of BP material to 2D material was confirmed by TEM characterization technique;Using SEM characterization technology,it is found that the particle size of Ag NPs increases with the increase of magnetron sputtering power,and the film uniformity is improved to some extent;By X-ray energy spectrum analysis(EDS)technology,it is found that there is P element in Al₂O₃/BP/Ag composite film,that is,the composite film is successfully prepared;UV-Vis technique was used to analyze the linear absorption characteristics of the samples,and obvious linear absorption characteristic peaks of BP could be observed.(2)The test results of femtosecond Z-scan technology show that:BP nanosheets,Al₂O₃/BP/Ag composite films,Al₂O₃/BP/PMMA/Ag composite films and Al₂O₃/BP/Al₂O₃/Ag composite films all exhibit saturated absorption characteristics.Compared with single BP nanosheets,the saturated absorption coefficient of Al₂O₃/BP/Ag composite films is significantly improved.Compared with Al₂O₃/BP/Ag composite films,it is found that the saturated absorption characteristics of Al₂O₃/BP/PMMA/Ag composite films and Al₂O₃/BP/Al₂O₃/Ag composite films have been significantly enhanced.(3)Theoretical analysis shows that:Under the action of light field,Ag NPs produce SP effect.The addition of PMMA and Al₂O₃ as two different polarization media enhances the local field effect,thus enhancing the saturated absorption characteristics of the composite film samples.It has been proved that the nonlinear absorption characteristics of the semiconducting BP material compounded with the noble metal Ag have been significantly improved,which makes it have important research significance in the field of optical components.