Investigation Of The Third Order Optical Nonlinearities In The Ag Crystals Doped Chalcogenide Glasses

Chalcogenide (chalcohalide) glasses have attracted the attention of many persons due to their ability to be used in infrared and nonlinear optics, especially for ternary chalcogenide GeS₂-Ga₂S₃ glasses and quarternary GeS₂-Ga₂S₃-Sb₂S₃ glasses, which have good optical properties , such as high third order optical nonlinearities, high refractive indices and transimission.In this thesis, we focus on the study of relations among the composition, structure and performances of ternary GeS₂-Ga₂S₃-AgCl glasses and quarternary GeS₂-Ga₂S₃-Sb₂S₃-AgCl glasses. The theories of optical nonlinearities, optical band gap, Z-scan and crystallization kinetics are reviewed in the first four chapters.In Chapter 5, iodine and iodide (CsI) were added to binary Ge-S glasses to compare their effects on physical and spectral properties. A series of samples containing different amounts of halogen and chalcogen elements were prepared. CsI decreased the glass transition temperature and increased thermal expansion to a greater extent than Iodine. However, the presence of iodine and CsI both have the effect of increasing density and have shifted the band-gap edge towards the far infrared region of the transmitted optical spectrum . Based on the Raman spectra, it can be speculated that both of the glassy nets are mainly constituted by the tetrahedral [GeS4-xIx]. By using the non-isothermal DTA method combined with the JMA and Augis-Bennett theories, the crystallization activation energy(E) are obtained.In Chapter 6, the GeGaSbS-AgCl glasses are first investigated. The result shows GeS₂-Ga₂S₃-Sb2S3-AgCl glass is characteristic with high value n2(1.581×10-10esu) , littleβat 800 nm(β=4.707cm/GW). The nonlinearity is attributed to high polarization of cation in the glass.The properties of GeS₂-Ga₂S₃ glass with AgCl are investigated in Chapter 7, (100-x)(0.9GeS2-0.1Ga₂S₃)-xAgCl (x=5,10,15 and 20 mol%) glass samples which also are prepared by the well-established melt-quenching technique have high transmission. The allowed direct transition,indirect transition and Urbach energy of samples were calculated according to the classical Tauc equation. Z-scan technique was carried out to investigate the third-order nonlinear optical properties of the samples. With increasing the AgCl content, the refractive indices and the third-order nonlinearity increase, molar refraction, metallization criterion and Urbach energy decrease. The effects of metallization criterion, optical band gap and Urbach energy on refractive indices of glass samples were also discussed. Then a series of GeS2-Ga2S3-AgCl chalcohalide 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 third order susceptibilityχ(3) is 6.411×10-11esu in the glasses, and that is 8.619×10-11 esu in the glass ceramics, which means glasse ceramics have better 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.