Study On Preparation And Nonlinear Optical Properties Of GeS₂-Ga₂S₃-Li₂S Glass-ceramics

Second-order nonlinearity materials have been applied in optical communications, optical modulation, and optical storage so on. Chalcogenide glass-ceramics, due to its low phonon energy, wide infrared transmission band, and easy preparation and processing, large nonlinear optical coefficients, make it a progressing second-order nonlinearity optical materials.In this paper, GeS2-Ga2S3-Li2S chalcogenide glasses were prepared by the conventional melt-quenching method, and glass-ceramics was induced. With the Maker fringe measurements, of the second-order nonlinearity in the chalcogenide glass-ceramics was studied.GeS2-Ga2S3-Li2S system glass has been investigated as fast ion conducting glass. However, the study of its optical nonlinearity is few, probably because of the difficulty of preparation. In this paper, GeS2-Ga2S3-Li2S chalcogenide glasses were prepared by using conventional melt-quenching method with elementary Li as raw materials. We prepared a series of chalcogenide glasses successfully and observed another glass-forming region besides the one in high lithium region, in the range of 6%—25% Li content. We focused our study on this area as the consideration of its glass-forming ability and second-order nonlinearity. The results indicated that glasses of this system have a relatively high glass transition temperature (above 400℃), high transmittance and good thermal stability.Two compositions (40GeS2-41GaS1.5-19Lio.5S and 56.5GeS2-37.5GaS1.5-6Lio.5S) were heat-treated to induce optical nonlinear crystals from the glasses, like Li2GaS2 and Li2Ga2GeS6. According to X-ray diffraction measurement, a-Ga2S3 was precipitated firstly. For longer durations of the heat treatment, characteristic XRD peaks of Li2Ga2GeS6 appeared. Only one crystal phase was precipitated in composition 40GeS2-41GaS1.5-19Lio.5S and it's in good agreement with the experimental data of Li2Ga2GeS6 crystal.By using Maker fringe method, the maximum SH intensity of (GGL6) was 1.5% of Z-cut quartz. And the shape of Maker matched well with theory. There was a tendency presented that the SH intensity was enhanced by the elongation of the heat-treating durations. The maximum value was as high as 0.35 of Z-cut quartz, the intensity declined to 0.3 of the reference. The maximumχ(2) of the samples was calculated to be about 1.763pm/V。By sides, we successfully synthesized Li2Ga2GeS6 crystals. By using Dark-field optical digit microscope, the average size was 0.3x0.25×0.3 (mm3).