Effect of substitution of S for Se on structure and physical properties in Ge<sub>11.5</sub>As<sub>24</sub>Se<sub>64.5–<i>x</i></sub>S<i><sub>x</sub></i> glass

Abstract

In this paper, chalcogenide glasses Ge<sub>11.5</sub>As<sub>24</sub>Se<sub>64.5–<i>x</i></sub>S<i><sub>x</sub></i> (<i>x</i> = 0, 16.125%, 32.25%, 48.375% and 64.5%) are prepared and their optical properties are studied in order to select the best components for the use in optical devices. The values of laser damage threshold, refractive index, and third-order nonlinear refractive index, as well as the absorption spectra of the glasses are measured. The results show that the linear and third-order nonlinear refractive indices of the glass decrease gradually, the glass optical band gap increases gradually, and the laser damage threshold increases continuously after the high threshold component S atoms have been introduced gradually. We further investigate the structural origins of these changes in physical properties by Raman scattering spectra and high resolution X-ray photoelectron spectroscopy. By analyzing the evolution process of different structural units in the glass, it is found that the heteropolar bonds (Ge—Se/S, As—Se/S) are dominant in these glass network structures, and compared with Se, and that Ge and As prefer to bond with S. As the ratio of S/Se increases, the number of chemical bonds related to Se (Ge—Se, As—Se and Se—Se) decreases gradually, while the number of chemical bonds related to Se (Ge—S, As—S and S—S) increases gradually, which has little effect on the change of the topological structure of glass. It can be concluded that the main reason for the change of physical properties of glass is the difference of the strength between chemical bonds in the glass structural system.