Study On The Third-Order Nonlinear Optical Properties Of CuS And Reduced Graphene Oxide Composites

Since the advent of the laser in 1960,optical technology has undergone revolutionary changes.While developing and enriching the optical discipline,an important branch of nonlinear optics has been established.Nonlinear optics has also developed rapidly since its establishment.At the same time,nonlinear optical materials are gradually applied in all part of people’s lives.Carbon materials,semiconductor nanomaterials,and metal materials are all popular nonlinear materials.In semiconductor nanomaterials,copper sulfide,as a self-doped p-type carrier transition metal sulfide,can prepare a variety of morphological structures,and can adjust its energy band gap,with excellent optical properties,and has a broad prospect in photoelectric applications.As an important derivative of graphene,graphene oxide has the same layered structure as graphene,excellent physical and chemical properties and unique nonlinear optical properties;the difference is that graphene oxide introduces a large number of oxygen-containing functional groups into each layer.And this structure makes graphene oxide have better activity and wider application space than graphene,such as better dispersion,hydrophilicity,more active,and easier to establish connections with other materials.Therefore,we use graphene oxide as a raw material to establish a connection with the copper sulfide material during the reduction process to form a composite material.And systematically study the nonlinear optical properties of copper sulfide and copper sulfide / reduced graphene oxide composites.The research work of this paper is mainly reflected in the following aspects:1.Copper sulfide microspheres were prepared by solvothermal method,and the optimal reaction preparation conditions were obtained by characterization and analysis of copper sulfide under different reaction conditions.The Cu S samples were characterized by X-ray diffractometer,scanning electron microscope and ultraviolet-visible absorption spectrometer.The characterization results showed that the prepared copper sulfide material was a flower-like microsphere structure,with a hexagonal phase structure,and has absorption in the visible and infrared regions.At the same time,the band gap of copper sulfide microspheres is estimated to be 1.55 e V according to the Kubelka-Munk formula.Under the condition that the excitation wavelength is 532 nm,a single-beam Z-scan was used to perform third-order nonlinear measurement of the copper sulfide material.The resulting open hole curve was a deep valley with centralsymmetry,and the closed hole curve was a valley-peak distribution.The third-order nonlinear absorption coefficient and the third-order nonlinear refractive index can be obtained through corresponding calculation formulas.Meanwhile,the imaginary part of the third-order nonlinear is much larger than the real part of the third-order nonlinear.Therefore,for copper sulfide microspheres,the third-order nonlinear absorption plays a dominant role in the third-order nonlinear optics.2.Copper sulfide and reduced graphene oxide composite materials were prepared by solvothermal method,and characterized by scanning electron microscope,transmission electron microscope and Fourier transform infrared spectroscopy.The analysis results show that copper sulfide microparticles adhere uniformly to the reduced graphene oxide and have stable bond formation.The single-beam Z-scan was used to test the composite material.The test results show that the copper sulfide / reduced graphene oxide composite material has the properties of reverse saturation absorption and self-defocusing.At the same time,we tested the third-order nonlinear optical properties of the composites with different proportions,and the final results show that as the concentration of reduced graphene oxide increases,the third-order nonlinear polarizability of the composite also increases.Compared with the third-order polarizability of copper sulfide,the third-order polarizability of the composite is improved by an order of magnitude,that is,the recombination of materials makes the third-order nonlinear optical properties have been improved to a certain extent.