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 (T-g), micro-hardness (H-v), 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 (E-g). The glass with the tightest network structure realized the lowest acoustic attenuation (alpha) 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 (M-2) of 209.78 x 10(-18)s(3)/g at 633 nm, which is close to 130 times greater than that of fused quartz.