Composition dependence of physical and optical properties in Ge-As-S chalcogenide glasses

•Composition dependence of properties in Ge-As-S glasses is investigated.•The density is linearly correlated with sulfur content.•A relation based on molar refractivity is derived to predict the refractive index.•A method based on diffuse reflectance is proposed to measure the optical bandgap.•Broad dependence of the optical bandgap on sulfur content is found.

The composition dependence of density (d), refractive index (n) and optical bandgap (Eg) of Ge-As-S chalcogenide glasses is investigated. It is shown that d correlates linearly with sulfur content but relatively poorly with the mean coordination number (MCN). It is also shown that n does not correlate directly with d, and instead a semi-empirical relation based on the molar refractivity (R) of Ge, As and S is derived, permitting to predict n from d with < 1% error. A convenient method based on diffuse reflectance is proposed to measure Eg of Ge-As-S glasses with good accuracy. It is shown that the value of Eg is dominated by the S content. These findings make it convenient to tailor the physical and optical properties of glasses in Ge-As-S system.