Investigation Of Third-order Nonlinear Optical Properties Of Ag₂Se And MoS₂ Nanomaterials

The new nanomaterial has many outstanding properties,so it raises the interests of the researchers and has been applied to various field.In these thirty years,the nanotechnology has improved rapidly,new preparation methods and measuring methods have appeared.In our research,we focus on the Ag₂Se quantum dots and MoS₂nanomaterials which are both metal chalcogenide nano-meter materials.The metal chalcogenide materials have some excellent properties and have been applied to many fields such as optics,thermology,electricity,magnetism,etc.We can find more applications by investigating their nonlinear optical properties.In addition,we investigated the nonlinear optical enhancement of the nanomaterial by surface plasmon resonance.This phenomenon can help us adjust the properties of the material and manufacture the new material with better properties.The main work of this thesis have been listed:1.We used the high resolution transmission electron microscopy to observe the shape of the Ag₂Se quantum dots and we found the fusion phenomenon of the quantum dots appeared.Then we investigated the nonlinear optical properties of the sample by Z-scan method.The results show that our sample have a relative large third-order nonlinear susceptibility and it has the potential to apply to photoelectric devices and optical switch.2.To find the mechanism of the large nonlinear optical phenomenon of the Ag₂Se quantum dots,we improved the laser power and found the diffraction rings showed up.The number of the rings increased when the laser power increased.But we couldn't figure out the number precisely,so we used ultrafast camera to shoot the dynamic process of the diffraction and found the rings distorted.At last,we explained the phenomenon through the spatial self-phase modulation theory,‘wind chime'model and the gravity effect.3.We investigated the nonlinear optical properties of the MoS₂ nanomaterial dispersing in the water.Then we placed some solution on the glass and some on the Au-nanorod arrays,after the water evaporated,we measured the third-order nonlinear optical susceptibility of these two sample.So we could find whether the Au-nanorod arrays were able to increase the nonlinear optical effect of the MoS₂ nanomaterial.The results show that the surface plasmon resonance happened and it can enhance the nonlinear optical effect of the nanomaterial.This technology can help us adjust the properties of the nanomaterials and can be used in material preparation field.