A Novel Technique Induced SHG Property In Ge-S Chalcogenide Glasses And Its Mechanism

Recent years,great attention was focused on the second harmonic generation(SHG)property induced in the glassy materials by different polarization methods,and a number of theories have been put forward to explain the phenomenon. Despite the various of polarization techniques,the mechanism behind the formation of the second-order nonlinearity has not yet reached a consensus with scholars from different countries. This project was based on the photo-induced anisotropy in chalcogenide glasses under the irradiation of sub-band gap light and the photo-induced fluidity. We mainly studied the laser power, polarization voltage, material composition and polarization mode, respectively, on the property of SHG and found out the best polarization condition. The relaxation process of the SHG property was also taken into consideration. The samples were characterized by some modern materials testing methods and obtained the evolve law after the polarization. This study was of great importance to analysis the root cause of SHG property in chalcogenide glasses and to discuss whether the physical models built in the oxide glass materials were also applied to the chalcogenide glass materials. It can broaden and enrich the research in this field and has vital value in scientific research and practical applications. The work provides a preliminary exploration for the development and design of the optoelectronic devices such as optical frequency multiplier and the all optical switch.In this thesis, GeS4 、GeS5 bulk chalcogenide glasses were prepared and studied their SHG property induced by the sub-band gap light auxiliary electric-field polarization technique. The main results are concluded as follows:(1) GeS4 、GeS5 bulk chalcogenide glasses were prepared by the melt-quench technique and their transmittance at the fundamental frequence 1064 nm and the double frequence 532 nm were 78.31%,74.73% and 59.53%,52.80%,respectively,which met the requirement of the experiment. Raman spectra shows the S8 ring peak strength in the GeS5 glass is greater than that in the GeS4 glass,which provides experimental basis to explain the effect of material composition changes on the SHG property.(2) Designed and set up the polarization device. Chalcogenide glasses were easily, cleanly, effectively polarized in air at room temperature. Meet the requirement of the applications in optoelectronic materials.(3) Mainly studied the laser power, polarization voltage, material composition and polarization mode, respectively, on the SHG property and explored out the best polarization condition. When polarized use the linear polarized mode,the direct frequency doubling waveguide was found in the Ge-S glasses. The relaxation process of the SHG property was also taken into consideration.(4) The samples were characterized by Raman scattering, Transmittance%,AFM,SEM, EDS and other modern materials testing methods. Explored the evolving law of the thermodynamics process in the samples before and after polarized.(5) The dipole orientation model was adopted to explain the mechanism of SHG property induced in the chalcogenide glasses. The allowed direct transition(Eoptd),indirect transition(Eopti)and Urbach energy(?E)of glass samples were calculated according to the classical Tauc equation. The effects of optical band gap, Urbach energy and the glass microstructure on SHG property were also discussed.