Spectral Absorption-emission Cross-Sections Ofâ…¡-â…¥ CdSe/ZnS (Core/Shell) Quantum Dot

In recent years, studies on semiconductor nanocrystals (quantum dots, QDs) develop rapidly in the world. The QDs including Ⅱ-Ⅵ, Ⅲ-Ⅳ, and IV-VI elements attract much attention due to their unique optical performance depending on sizes. At present, QDs and their applications have become a research hotspot in the field of optical amplification, life sciences, and lighting.This dissertation includes the following aspects:(1) We begin with an overview of brief history and applications of QD materials, including the selection of QD materials QD structures, optical properties,and QD applied developments in the field of optical device, following description of developing prospect of QD doped fiber amplifiers and QD doped lasers in the future.(2) Due to emission peaks locating in visible band (465～640nm), it is favorable for CdSe/ZnS QD used as optical gain media to form sub-white light lasers and optical amplifiers based on optical fiber technologies. In chapter two, we discuss absorption and emission spectral characteristics of CdSe/ZnS QD, optical characterizing methods. Then, two preparation methods of CdSe/ZnS QD are described, one of which is organometallic synthesis, and another is strain self-assembly method.(3) In chapter three, we compare some of methods for measuring absorption cross sections, e.g., two-photon absorption and spectrophotometric method. Then, the size depending peak-absorption cross section of the CdSe/ZnS QD are estimated by using the spectrophotometric method.(4) A simple and accurate method to determine spectrum absorption-emission cross-sections of QDs is presented in chapter four. By using this method, the absorption cross-sections of CdSe/ZnS QDs in different sizes are determined according to Lambert-Beer’s law and the measured first absorption spectra of the QDs. Then, the emission cross-sections are determined according to the Mc Cumber theory and normalizing both the measured absorption peaks and emission peaks. As an example, the cross-sections of CdSe/ZnS QDs in two sizes are obtained, one of which the emission peak locates at530nm, and another at615nm. The obtained cross-sections are available for investigating QD optical gain and excited emission for further configuring novel QD optoelectronic devices in the future.