Research On High-efficiency Deposition And Optical Nonlinearity Of 2D Transition Metal Dichalcogenides

Nonlinear optics is an important filed in photonics.In the 21^st century,the study of nonlinear optical materials has evolved from macroscopic materials into nano-materials.Since the discovery of graphene in 2004,many two-dimension?2D?materials including graphene,graphene oxide,topological insulators,transition metal carbides and transition metal dichalcogenides?TMDs?have attracted wide attention and research interest.Two-dimension material is a kind of material which contains only a single layer or few layers planar mesh atomic structure units.These materials have many optical nonlinear properties including saturable absorption characteristics,Kerr nonlinear effect and so on.These features can be used for tuning Q-switched lasers,mode-locked lasers,optical modulators and many other instruments.In varieties of ways to explore optical nonlinearity of 2D materials,depositing materials onto the side of tapered fiber has many advantages like simple operation,low cost and longer interaction distance between fiber and the 2D materials than other methods.However,the traditional method of depositing has some drawbacks.For example,the deposition rate is too slow,the deposition process is hard to control,and it is required to provide a high optical power to drive the deposition process.In this thesis,a new method caled ethanol catalytic deposition?ECD?is proposed to offer a better way for deposition of 2D materials.Comparing with the traditional optical driven deposition method,the new ECD method can significantly improve the deposition rate,reduce the light power threshold and make the deposition process under control.In addition,ECD method is well studied through series of contrast experiments and the factors that affect the deposition process including diameter of tapered fiber,input optical power,the concentration of dispersion and many other factors are discussed.After optimizing the ECD methods,we have conducted series of research works on optical nonlinearity of 2D TMDs from three respects,including research on saturable absorption of TMDs,designing and tuning Q-switched laser based on TMDs as saturable absorber and light modulator design.2D materials have been proved good saturable absorption characteristics and photo induced refractive index change characteristics.It is believed that 2D materials can have wide potential applications in the future similar to what graphene has brought.