The effects of germanium addition on properties of Ga-Sb-S chalcogenide glasses

• Property and structure evolutions of Ga(8-x)GexSb32S60 glasses are investigated.
• Glass thermal stability becomes optimum when x = 4.
• Optical bandgap decreases remarkably when Ge is added to the Ga-based glass.
• Infrared cut-off edge shifts to the shorter wavelength side with increasing x.
• Density, linear and nonlinear refractive index decrease with increasing x.

Properties of the glasses are experimentally investigated when Ga is gradually substituted by Ge in Ga8Sb32S60 chalcogenide glass. The glass structure is also studied to elucidate the variations of the properties. While the substitution of Ga by Ge does not remarkably change the glass transition temperature Tg, the thermal stability against crystallization becomes optimum when half of the Ga atoms are replaced by Ge atoms. The short-wavelength absorption edge λS (or optical bandgap Eg) exhibits a remarkable decrease when a small amount of Ge is added, however, its value does not change significantly with further Ga substitution. As Ga is gradually replaced by Ge, the long-wavelength cut-off edge λL, the density ρ, the linear refractive index n, and the third-order nonlinear refractive index n2 decrease. It is shown that the property variations of the glasses could be explained by the evolution of the glass structure.