Studies On Third-order Nonlinear Optical Properties Of Graphene Composite Materials

Nonlinear optics has great influence on the laser technology, spectroscopy, photochemistry and many other disciplines. Nonlinear optical materials is anecessary basic material in many fields development. With the rapid development of optical communication technology, instrumentation demands for the nonlinear optical materials more and more high, explore and synthesis performance nonlinear optical materials has become a very important research direction.Semiconductor nanomaterials due to their unique optical and electrical properties, show broad application prospect in the field of optoelectronic devices and functional materials, has become a research interest in nano system. However, smaller size of semiconductor nano materials, poor dispersion and stability, it needs to be modified on the surface of other’s materials by physical pathway or chemical method for synthesizing composite materials. Composite materials of modified can prevent the agglomeration of nanomaterials, improve the dispersion and perfect the properties of the materials. If the two kinds of materials with nonlinear response, the third-order nonlinear optical properties of the composite materials may be improved.Graphene is a two-dimensional honeycomb material, composed by a single layer of carbon atoms arranged periodically; with electricity, heat, mechanical properties, high surface area and excellent functiongal characteristics and excellent performance; widely concerned by the material, energy, environment, medicine, physics, chemistry, biology and other fields. It is the hot topic in the current international research. The plane stable structure and strong electron transfer and migration ability, make it become the ideal carrier of semiconductor materials. The study and preparation of graphene/semico-nductor composite materials has become a new focus, and has made a great achievement.This paper is divided into four chapters, the first chapter briefly introduces the theory of nonlinear optics, the research and development of nonlinear optical materials and the method of testing its third-order nonlinear, and the research of the II-VI semiconductor material, graphene oxide and graphene are reviewed; the second chapter mainly characterized of graphene oxide, and the third-order nonlinear optical properties of graphene oxide and the reduction of graphene oxide; the third and the four chapter for the characterization of graphene/ZnxCd1-xS composite materials, and investigated the nonlinear optical properties of graphen /CdS by using Z- scan method.The main research results are briefly listed as follows:1.Good degree of the graphene oxide was prepared by using improved hummers method,which proposed by Daniela C. Marcano, and the reduced graphene oxide was prepared with dimethyl sulfoxide as a reducing agent; the third-order nonlinear property of the materials were measured by picosecond Z-scan system. At the wavelength of 532 nm, the pulse width of 30 ps, the energy of 1.25 μJ, graphene oxide has a positive nonlinear refractive index and properties of reverse saturable absorption, the reduced the graphene oxide has a positive nonlinear refractive index and properties of saturable absorption.2. Graphene-CdS composites were synthesized by a solvothermal method. The composites were characterized by X-ray diffraction, transmission electron microscopy and UV–vis absorption on their structure, size and morphology, which demonstrated that cadmium sulfide quantum dots with an average diameter of about 7 nm attached to the graphene surface. The third-order nonlinear property of the composites materials were measured by picosecond Z-scan system. The results showed that grapheme-CdS composite has a positive nonlinear refractive index and properties of saturable absorption at this condition. Compared with cadmium sulfide quantum dots, the third-order nonlinear of composites were improved. As an extension of the experiment, Graphen/ZnxCd1-xS( x= 0.2, 0.5, 0.8, 1) composites were synthesized by a solvothermal method, characterization results showed that the composite material has sphalerite structure.At last, the deficiencies of this work is illustrated and the next step of work content and experiment are presented.