Investigation Of The Third Order Optical Nonlinearities In The Nano-particles Doped Chalcogenide Glasses

In recent years, materials with large third-order nonlinearity have been investigated extensively for their ability to be utilized in ultrafast all-optical switching in optical communication network. More and more people began to pay attention on chalcogenide and chalconhalide glasses because of their small phonon energies, little probability of multiphonon relaxation , large third-order nonlinear susceptibilityχ³ (about two or three orders of magnitude larger than that of silica glass)and fast response time. However, compared to oxide glasses, chalcogenide glasses have relatively weak mechanical properties with high thermal expansion coefficient and low resistance to thermal shock. Consequently it is difficult to optimize the design of infrared systems using these glasses.In this thesis, we focus on the study of relations among the composition, strutrue, properties and optical nonlinearity of ternary GeS₂-Ga₂S₃-CsCl glasses and GeS₂-Ga₂S₃-PbCl₂ glasses. Chosen the best host to heat treated formicro-crystalline.Analysis the relationships of properties, mechanical properties and optical nonlinearity between precursor glass and its glass ceramicsThe purpose and significance of the dissertation are summed up in Chapter one. Following the overview the development of investigation on optical nonlinearity, the latest development and application of the chalcogenide glasses and chalconhalide glasses Cceramics is reviewed. The theories of optical nonlinearities, optical band gap, and Z-scan and crystallization kinetics are reviewed in the fist chapter.In Chapter 4, the GeS₂-Ga₂S₃-CsCl glass-ceramic is prepared and studied. The X-ray diffraction and scanning electron microscope results confirm the formations of Ga₂S₃ phase grains with size of 50–100 nm. Z-scan technology was employed to investigate the third-order nonlinear optical characteristics of both precursor glass and its glass ceramics at 800nm. The results show that nonlinear refractive index n₂ as well as nonlinear absorption coefficientβincrease after heat treatment, which is due to quantum effects, and the largest nonlinear refraction coefficient n₂ of the glass ceramics is 4.341×10^-11esu which is 4 times larger than that of the host. In chapter 5, a series of (100-x)(75GeS₂-25Ga₂S₃)-xPbCl₂(x=0,5,10,15mol%) chalcogenide glasses were prepared by conventional melt-quenching method. The physical and optical properties (densities, refractive indices, absorption spectra and transmission spectra) were determined. Z-scan technique was carried out to investigate the third-order nonlinear optical properties of the samples. The effect of PbCl₂ content on the linear refractive index, transmission property, and third-order nonlinear property of samples has been investigated. The result shows that the linear refractive index nonlinear refractive index, nonlinear absorption coefficient and third-order nonlinear optical susceptibility of samples increases with PbCl₂ content.GeS₂-Ga₂S₃–PbCl₂ chalconhalide glasses are investigated in Chapter 6. Thermal properties were measured by Differential Thermal Analysis (DTA). From the heating-rate dependency of crystallization temperature, the activation energy for crystallization (E) and the order parameter (n) were calculated by the Kissinger equation. The results show that the glasses have good thermal stability and most probable mechanism is volume controlled one-dimensional growth. It seems that 65GeS₂-25Ga₂S₃–10 PbCl₂ glass is a promising candidate for making transparent neoceramic glass.Then a series of 65GeS₂-25Ga₂S₃–10 PbCl₂ chalconhalide glasses are heat-treated to get glass-ceramic. We change the annealing time to control the crystallization in the experiment. We test the good performance of the glass sample including density, micro-hardness, XRD-ray diffraction and spectroscopy, and character the internal nano-crystalline of glass-ceramics. The result shows that glasses ceramics have better mechanical properties and optical nonlinearities. The conclusions of the study are presented in the last chapter, and some investigations which should be conducted in future are also listed.