Second-order Optical Nonlinearity Of GeS₂-based Chalcogenide Glasses And Films

In order to exploit high performance second-order nonlinear optical materials, and also to enrich and develop the theoretical knowledge on the nonlinear optics, various GeS₂ and/or Ga₂S₃ based glasses combined with different pnicogen chalcogenides were studied by X-ray diffraction (XRD), differential scanning calorimetry-thermogravimetry (DSC-TG), ultraviolet-visible-NIR spectroscopy (UV-Vis-NIR), infrared(IR) spectroscopy and Raman spectroscopy techniques. After poling the glasses by the electric/temperature-field and electron-beam irradiation, the SHG properties of the glasses were characterized by the Maker Fringe. The relaxation time of the glasses was tested by the thermally stimulated depolarization current (TSDC) technique. Relationship between the structure and the SHG of glasses has been studied systemically.The experimental results show that the xGeS₂·(1-x)P₂S₅ glasses poled by electric/temperature -field show large second-order optical nonlinearity (SON) due to the existance of many kinds of anion groups. These anion groups can be oriented in a particular direction, which break the centrosymmetry and isotropy of glasses and lead to the large SON in the glasses.There are many metal bonds, homobonds, or other polarized covalent bonds in the xGeS₂·(1-x)Sb₂S₃ glasses. These defects can act as a particular dipole, and can be recombined and reoriented after electric/temperature -field poling (ETFP), lead to large SON. At the same time, as the transmittance of the glass in the visible light region is not very high, the reflecting SHG can be observed.The (1-x-y)GeS₂·xGa₂S₃·ySb₂S₃ glasses with low Sb₂S₃ have a relatively high transmittance in the visible light region, showing transmitting SHG; and the transmittance is decreased with increasing Sb₂S₃, showing both the transmitting and reflecting SHG. The glasses with higher Sb₂S₃ show only the reflecting SHG. The theoretical study show that the different transmittance of the glass in the visible light region will lead to the transmitting SHG and reflecting SHG. respectively.