Composition dependence of the physical and acousto-optic properties of transparent Ge–As–S chalcogenide glasses

Three groups of Ge–As–S glasses with compositions of (I) GexAs40−xS60 (x = 25, 30, 35 at.%), (II) GexAs10S90−x (x = 25, 30, 35 at.%) and (III) Ge30AsxS70−x (x = 5, 10, 15 at.%) were studied to understand the role of glass composition in determining physical and acousto-optic properties. For each group of glasses, the glass transition temperature (Tg), micro-hardness (Hv), elastic modulus and acoustic velocity increased with the addition of Ge, and the elements that determine the magnitude of performance variation are Ge > As > S. All glass samples had optical transmission higher than 54% at 633 nm, and the level of sulfur content determined the value of the optical bandgap (Eg). The glass with the tightest network structure realized the lowest acoustic attenuation (α) of 1.49 dB/cm at 25 MHz ultrasonic frequency. Furthermore, the maximum refractive index (n = 2.482) in Ge30As15S55 glass contributed to the maximum acousto-optic figure of merit (M2) of 209.78 × 10−18 s3/g at 633 nm, which is close to 130 times greater than that of fused quartz