Study On Preparation, Structure And Properties Of Nonlinear Optical Glasses In The GeS₂-Ga₂S₃-CdS System

Nonlinear optical material is one kind of the key materials in optical communication, and may have extensive uses in the fields of all optical disposing and photon computer. Glass is one kind of new nonlinear optical materials. Chalcogenide glasses have larger nonlinear optical coefficient than ordinary oxide glasses, therefore, there investigations are one of the attractive subjects at present. Ge—Ga—S system glasses have good thermal durability, chemical durability and relatively high transparency in the visible region. It is easy to induce structural defects by change glass composition and finally increase the nonlinearity. So, study of GeS₂-Ga₂S₃-CdS nonlinear optical glasses is considerable important from the scientific and practical views.Glasses in GeS₂-Ga₂S₃-CdS pseudo-ternary system was prepared by conventional melt quenching technique. Utilizing the techniques such as electron probe microanalysis (EPMA) , X-Ray diffraction, Raman spectra, Comprehensive thermal analysis, UV-Vis-IR spectra, and etc., research has been made systematically on the relationship of composition, structure and properties of glasses in the GeS₂-Ga₂S₃-CdS pseudo-ternary system. Femtosecond time-resolved optical Kerr gate technique has been used to analyze the third-order nonlinear optical property and the relationship between the third-order nonlinear property and structure. Utilizing Maker fringe method, second-harmonic generation (SHG) has been investigated on the glasses within this system glasses through heat-auxiliary-electric-field polarizing technique.Based on the previous work, the glass-forming region of GeS₂-Ga₂S3-CdS pseudo-ternary system is determined. The glass transition temperatures range from 375-436℃ and the composition with the best glass formation ability is 90GeS₂·5Ga₂S₃-5CdS. From the analysis on the relationship between composition, structure and properties in the GeS₂-Ga₂S₃-CdS pseudo-ternary system, the basic s.u. forming the glass network are [GeS_4/2], [GaS_4/2] tetrahedra and ethane-like units [S₃Ge(Ga)-(Ga)GeS₃], which are connected by corner-shared and edge-shared mode to form a three-dimensional network. CdS can bring some non-bridge sulfur to decrease the degree of aggregation.GeS₂-Ga₂S₃-CdS pseudo-ternary chalcogenide glasses have large and ultrafast third-order optical nonlinearity. The experimental results show that all OKE signals are symmetrical at origin, the full width at half maximum (FWHM) of the OKE signals are 150 fs, x⁽³⁾ has inverse ratio with amount of defects in glass and its maximum is 10^-12esu. The third-order optical nonlinearity has not linear relationship with the linear refraction index n. The laser irradiation-enhancement on OKE signals of glasses was found and attributed to the reorientation of the IVAP (Intimate Valence Alteration Pairs) along the pump beam and resulted in the anisotropic.Maker-fringes with good symmetry has been observed within the GeS₂-Ga₂S₃-CdS glasses after electrical poling, and the maximum of relative SHG intensities appears at an incidence angle around ±(40-50)°. Investigations on dependence of SHG with glass composition, structure and poling conditions indicate that the SHG intensity have tight relation with poling conditions. Under the poling condition conducted with 5kV, 280°C and 30min, the maximum of second-order nonlinear susceptibility x⁽²⁾ =4.36pm/V for 70GeS₂·15Ga₂S₃-15CdS glass. The mechanism of SHG, the influences of poling conditions and glass compositions are explained by model of dipoles. It was found that the effective poled region is located at several microns under surface of anode and the SHG have good durability at room temperature.