Non-equivalent interchange between acousto-optic performance and laser damage resistance in an eco-friendly Ge-Sn-Se-S quaternary chalcogenide glass system

The design and development of high-performance acousto-optic materials are driving the large-scale application of acousto-optic modulation technology in key fields such as optical communication and laser radar. Although commercial chalcogenide glasses (ChGs; e.g., As₂S₃, As₂Se₃, Ge₃₃As₁₂Se₅₅, etc.) had been found to exhibit excellent acousto-optic properties, their practical applications are limited by a low laser-induced damage threshold (<i>LIDT</i>), insufficient mechanical strength, and the formation of toxic oxide byproducts from arsenic. To this end, we develop and design a quaternary, eco-friendly Ge-Sn-Se-S (GSSS) ChG system based on a robust Ge and Sn tetrahedral network. Through a graded S/Se interchange strategy, rigid [GeS_nSe_4-n] and [SnS_nSe_4-n] tetrahedra are formed and dominate within the glass network. This not only boosts <i>LIDT</i> to 13.89 J/cm²-about 8.7 times that of As₂S₃, but also drastically reduces the acoustic attenuation coefficient (α), bringing it down to 1.21 dB/cm at 10 MHz which is 84.2% lower than As₂S₃ glass (7.65 dB/cm at 10 MHz). Although the acousto-optic figure of merit (<i>M</i>₂) of the GSSS ChGs decreases with S/Se ratio, its minimum value is 211.8 × 10^-18s³/g at 1.55 µm, still surpassing that of As₂S₃ glass (182.54×10^-18s³/g at 1.55 µm) by 16%. These findings highlight the exceptional potential of GSSS ChGs for developing high-performance, environmentally friendly acousto-optic devices.