A Study Of Optical Characteristics Of CdSe, CdSe/ZnS And PbSe Quantum Dots And Quantum Dot-Doped Fiber Amplifier

Semiconductor colloidal quantum dots (QDs) are studied by experimentally and theoretically. The attention is owed not only to academic interest in a system which demonstrates quantum mechanical effects and lies in a realm between bulk and atomic properties, but also because of its possible applications in medicines, optoelectronics and biology techniques. This dissertation focuses on the studies on the optical characteristics of QDs and an initial probe of their applications in optical communication systems. It is of great significance in improving the optical fiber amplifiers on bandwidth and noise in the telecommunication systems by mixing QDs into a hollow fiber to form a quantum dot-doped fiber amplifier (QDFA).Beginning with reviewing the developments of optical communication, the basic principle of QDFA is discussed in the first chapter. Following describing the basic concept of QDs in quantum mechanics in chapter 2, we discuss quantum structures, fluorescence characteristics and synthesis methods, the applications of QDs in optoelectronic technologies. Chapter 3 is devoted to the measured the absorption-emission spectra of 3.0-nm CdSe (core), 3.85-nm CdSe/ZnS (core/shell) and 5.5-nm PbSe (core) QDs, their first absorption wavelength located in a visible, ultraviolet and near-infrared wave band, respectively. The peak value of the absorption cross-sections of CdSe, CdSe/ZnS and PbSe QDs are determined by Beer-Lambert law based on the sample concentrations and the diameters of the QDs. A comparison of the refractive index between pure solvents and colloid (QDs in solvents) is also involved in chapter 3. In chapter 4, the prefabrication of the doped background materials used in a fiber core is presented, based on it, the QD fiber can be prepared in a laboratory. Chapter 5 covers the potential applications of QDFA, and the remained issues (for example, scattering losses, stabilities of the QDs, and the temperature-independent energy spectra) required to be solved in the future are also discussed finally.