Nonlinear Optical Properties Of Composite Films Base On ZnSe/ZnS Core-shell Quantum Dots

In order to broaden the application of ZnSe/ZnS quantum dots in the field of optoelectronic devices and explore the nonlinear absorption characteristics and mechanism of ZnSe/ZnS quantum dots in nanofilms,this paper firstly prepared ZnSe/ZnS quantum dots by two-step method,and further prepared Al₂O₃/Ag/ZnSe/ZnS and Al₂O₃/PMMA/ZnSe/ZnS two different system composite films by magnetron sputtering technology and spin coating technology.By means of transmission electron microscope(TEM),element energy spectrum analyzer(EDS),scanning electron microscope(SEM),UV-vis absorption spectroscopy techniques analysis of the related preparation conditions on the morphology structure of the sample and the influence of the linear absorption characteristics.At the same time using femtosecond Z scan testing technology to explore the nonlinear optical properties and nonlinear absorption mechanism of two different system composite films.The main results are as follows:The solution of ZnSe/ZnS quantum dots was successfully prepared by two-step method.TEM observation showed that the quantum dots were spherical with a size of 4.3nm and uniform distribution.Through Z-scan testing technology,it is found that the nonlinear absorption type of quantum dots was saturated absorption.When the concentration of quantum dots increases,the saturation absorption characteristics gradually increase,but when the concentration of quantum dots reaches 1.0mg/ml,the cluster phenomenon occurs,which inhibits the further enhancement of the nonlinear absorption characteristics.Al₂O₃/Ag/ZnSe/ZnS and Al₂O₃/PMMA/ZnSe/ZnS composite films of ZnSe/ZnS quantum dots had been successfully prepared by magnetron sputtering and spin-coating techniques.The surface of the composite films were compact.The linear optical properties of the composite films had been analyzed by Uv-vis absorption spectrum.From the linear absorption spectrum,it was found that the absorption peaks of two composite films were located at 396nm and 355nm,respectively.Composite films which modified with Ag produce surface plasmon effect and local field enhancement effect,and linear absorption was enhanced.The nonlinear measurement and analysis of the composite films were carried out by open aperture Z scan technology.The result shows that Al₂O₃/Ag/ZnSe/ZnS composite films exhibited saturated absorption characteristics,and the saturation absorption characteristics can be enhanced by increasing Ag sputtering power and the concentration of quantum dots.For Al₂O₃/PMMA/ZnSe/ZnS composite films,the nonlinear absorption types can be changed by changing the PMMA content or quantum dots concentration.The nonlinear absorption coefficients of ZnSe/ZnS quantum dots were improved after modified by Ag or PMMA,and the nonlinear characteristics of ZnSe/ZnS quantum dots modified by Ag were enhanced more obviously,which broaden the application of quantum dots in the field of optoelectronic devices.