Nonlinear Optical Properties Of Composite Films Base OM ZnSe/ZnS Core-Shell Quantum Dots

Optical materials with large third-order nonlinear optical coefficients have great potential for applications in nonlinear optical devices such as saturable absorbers,optical switches,optical limiters,and wavelength converters.With the increasing demand for optical information processing,how to enhance the optical properties of materials has become a major research direction.WTe₂ has a high unsaturated magnetoresistance and good superconductivity at high voltage,which makes them a broad application prospect in future applications of spintronics and optoelectronic devices.Compared with single semiconductor materials,the nonlinear optical properties of metal-semiconductor composite and doped systems materials are significantly improved,which provides new ideas for the application of semiconductors in optoelectronic devices.In this paper,WTe₂ thin films,Ag/WTe₂ composite films,Ag-WTe₂ nanofilms,and Ni-WTe₂ nanofilms were successfully prepared.The morphology and linear optical properties of the samples were characterized by SEM,AFM,UV-Vis absorption spectroscopy,and Raman spectroscopy tests.The effect of sputtering power and other parameters on the nonlinear optical properties of the sample is investigated by the picosecond Z-scan test technique,and the nonlinear absorption characteristics of the samples are also illustrated with the mechanism diagram.The following results were obtained.WTe₂ films,Ag/WTe₂ composite films,Ag-WTe₂ nanofilms,and Ni-WTe₂nanofilms with different sputtering powers were prepared by magnetron sputtering.The analysis of the characterization results shows that the particle size of different thin film samples is positively correlated with the sputtering power,and the films become dense as the power increases.The Raman test results showed that the prepared WTe₂ films were not monolayer or few-layer films.The UV-vis absorption spectra showed that the band gap of Ag/WTe₂ composite films increased compared with that of single WTe₂ films,and the band gaps of Ag-WTe₂ nanofilms and Ni-WTe₂ nanofilms decreased compared with that of single WTe₂ films.The open-hole Z-scan test results show that the WTe₂ films,Ag/WTe₂ composite films,Ag-WTe₂ nanofilms,and Ni-WTe₂ nanofilms exhibit saturable absorption properties.Except for Ag-WTe₂ nanofilms,the saturable absorption properties of all the thin film samples are enhanced with increasing sputtering power.The variation of the incident laser energy also affects the nonlinear absorption properties of the samples.A reasonable energy level structure diagram is constructed to provide a reasonable explanation for the variation of the nonlinear absorption properties of the samples.It is demonstrated that the nonlinear optical properties of the metal-semiconductor composite and doped systems are significantly enhanced compared to those of single semiconductor materials.The application area of semiconductor materials in optoelectronic devices is broadened.