Investigation Of Third Order Optical Nonlinearities In Transparent Bismuth Glass Ceramics

In this paper, we focus on the studies of the formation range and third-order nonlinear optical properties of the Bi₂O₃-B₂O₃-WO₃ and Bi₂O₃-B₂O₃-Ga₂O₃ systems. The thermal property of Bi₂O₃-B₂O₃-Ga₂O₃-TiO₂ glasses and the third-order nonlinear properties of the samples after heat treatment were investigated.The purpose, significance and main contents of this dissertation are summed up in Chapter one. Following the overview the characteristics, application and latest development of the bismuth oxide-based glasses and glass ceramics are reviewed. The theories of the third order optical nonlinearity and the characteristics of nonlinear optical materials are also included.In chapter two, the theory and experimental method of Z-scan technique are introduced. The methods of improved Z-scan measurement and scan sensitivity are also discussed. Z-scan experimental setup is presented in the laboratory. The realization of auto-control makes the measurement more convenient and reliable.In chapter three, the extrapolation to obtain optical band gap, Urbach energy and crystallization activation energy are introduced. The value of optical band gap can be derived from plot of (α(ω)ω)1/2 against photon energyωin eV by extrapolating the linear portions to zero absorption, and Urbach energy is calculated from the slope of straight line in plot of ln(α) vs. photon energyωin eV. The thermal stability of glasses can be characterized by the difference between crystallization temperature and glass transition temperature. The crystallization activation energy can be derived from the methods of Kissinger and Augis-Bennett.In the fourth chapter, the third-order nonlinear optical properties of Bi₂O₃-B₂O₃-WO₃ glass system were studied. The formation range of the ternary system was investigated firstly. The density, refractive index and third-order nonlinearity optical properties of glass samples were measured. The conclusions were as follows: The densities, refractive indexes and third-order nonlinear coefficients of samples increased with the increase of WO3 content.In chapter five, the formation range of ternary Bi₂O₃-B₂O₃-Ga₂O₃ glass system was studied. This ternary glass system has large domain. The optical properties (refractive index, third-order nonlinearity et al) of glass samples were investigated. The third-order nonlinear optical properties were measured by Z-method. The refractive index and third-order nonlinear refractive index of the glasses increased with increasing Ga2O3 content. In chapter six, the thermal properties of Bi₂O₃-B2O3-Ga2O3-TiO2 glass samples were studied. The Bi12TiO20 nanocrystals embedded glass ceramics were produced by treating the 70Bi₂O₃-20B₂O₃-5Ga₂O₃-5TiO₂ glass sample at 450℃for 9 hours. The crystallite sizes were calculated from XRD and SEM data. Both refractive index and density increase with increasing heat treatment time, and transparence of visible bands were weakened after heat treatment. The value of third-order nonlinear refractive index of glass increased after heat-treating.At the last, all results of present work are outlined, and some investigations which should be carried out in the future are also discussed.