Studies Of The Optical Characteristic Of Quantum Confined Structure

The study on the optical characteristics of TiO₂ quantum confined structure and the characteristics of heavy- and light-hole quantum beat of degenerated four-wave mixing in In_x Ga_1-x N/GaN quantum well are presented in this thesis.In the first place, the research background, the future in application, the physical characteristics, the method in quantum confined structure have been summarized.In the second place, TiO₂ nano-particle films coated with and without CF have been prepared by forced hydrolysis and magnetron sputtering respectively. It has been showed by Raman spectra that the samples were mixtures of anatase and ratile. The red shift of Raman spectra have been found in some nano-TiO₂/CF film samples, which was analyzed and discussed. The broad photoluminescence has been observed under below-band-gap excitation at room temperature. A sharp and intense up-converted line at 429.8nm newly appears in two kinds of samples. The largeinterface roughness of the nano-particles is responsible for the appearance ofsurface states localized between conduction band and valence band. These intermediate states provide great possibility to observe a rather strong up-conversion photoluminescence signal. This up-conversion process is analyzed.In the third place, the characteristics of heavy- and light-hole quantum beat of degenerated four-wave mixing in In_x Ga_1-x N/GaN quantum well have been analyzed by solving the Bloch equations. The model used for describing the phenomena can be considered as a three-level model consisting of the ground state and two excited states. It is shown that the intensity of the oscillation detected in degenerated four-wave mixing is modulated with real time and has the typical characteristics of quantum beat. The period of the beat increase with the increase of In content and the intensity of the beat has great dependence on dephasing rate.