Study On Nonlinear Optical Effects Of The Water Soluble Cdte And CDTE/ZNSE Quantum Dots

In recent years, the study on the preparation and the optical properties of quantum dots have became a hot spot, quantum dots are three-dimensional restricted materials, and they have a lot of physical and chemical properties. Because of the quantum dots have unique quantum effects, its nonlinear absorption coefficient and nonlinear refractive index are bigger than other materials, quantum dots can be widely used in optical limiting light opening aspects.This article is mainly to study on the nonlinear phenomena of the water-soluble CdTe and CdTe/ZnSe quantum dots. In the first chapter, we introduced the concept of quantum dots, several quantum effects and the research status. In the second chapter, we briefly described several measurement methods of nonlinear optical properties, wherein, Z-Scan method is the first choice for the experiment method. In the third chapter, we described how to prepare the water-soluble CdTe and CdTe/ZnSe quantum dots, and measured the absorption and fluorescence spectra of ten kinds of samples. In the fourth chapter, it is the experimental part, the light source we used was800nm wavelength of the Ti:Sapphire laser. And the experiment which we choose to study the nonlinear optical properties of water-soluble CdTe and CdTe/ZnSe is Z-Scan experiment.Through calculated the experimental curve, we found the nonlinear absorption coefficient and refractive index of water-soluble CdTe and CdTe/ZnSe quantum dots are positive. First we did open-pore Z-scan on CdTe quantum dots, and calculated the nonlinear absorption coefficient by varying the incident light intensity and sample size, then we found two-photon absorption is the main reason to caused that. After that we compared the water-soluble CdTe and of CdTe/ZnSe quantum dots nonlinear absorption coefficient and nonlinear refractive index, we found the refractive index of the CdTe/ZnSe quantum dots is1.2times to CdTe quantum dots, because of the CdTe quantum dot surface cladding, so the concentration of surface defects of the quantum dots was reduced effectively, finally got bigger nonlinear refractive index.