Recently, Zhenfei Cao (first author), a postgraduate student in our laboratory, and professor Shixun Dai (corresponding author) have published an article entitled “Correlation between acousto-optic and structural properties of Ge–Sb–S chalcogenide glasses” in Ceramics International (Ceramics International. 2020, 46(8), 10385-10391. https://doi.org/10.1016/j.ceramint.2020.01.036).

       Acousto-optic interaction has been widely used in basic acousto-optic devices such as laser beam deflection and modulation with the development of optical communication technology, micro-acoustic technology and acousto-optic materials. In order to further improve the performance of various acousto-optic devices, new and high-quality acousto-optic materials have become research hotspots. Chalcogenide glasses possess attractive acousto-optic properties with high figure of merit M₂, because of their high refractive index and low acoustic velocity. To date, the most widely studied acousto-optic materials are mainly concentrated in As-containing chalcogenide glasses in the near-infrared band. In order to explore safe and environmental acousto-optic materials, Ge–Sb–S glasses were prepared and their thermomechanical, elastic, acoustic and optical properties were studied completely. Two series glass compositions were selected and distinguished by two lines: (a) (100–x) GeS₂-xSb₂S₃and (b) Ge₁₂Sb_yS_88-y. The acousto-optic figures of merit (M₂) of the glasses were calculated using these above measured parameters and the Raman spectra of the glasses (Fig. 1) were measured to explore the relationship between the acousto-optic properties and the changes in the internal structures of the glasses. The study found that in the first series, the increase in Sb₂S₃ content and the decrease in GeS₄tetrahedral units led to a decrease in the stability of the glass and an increase in acoustic attenuation (Fig. 2a). Meantime, the refractive index increases with increased Sb element, greatly increasing the value of M₂ (Table 1). In the second series, the internal structure of the glass changed from loose to dense which caused the acoustic attenuation to decrease (Fig. 2b) and M₂ to increase (Table 1) with increased Sb content. In this series of samples, Ge₁₂Sb₃₂S₅₆ glass obtained the highest value of M₂ at 1550 nm (M₂ = 252 ´ 10^-18 s³/g) and the corresponding acoustic attenuation at 25 MHz ultrasonic frequency was 1.95 dB/cm, which effectively achieved the purpose of compromise between high acousto-optic figure of merit and low acoustic attenuation.

Fig. 1: Raman spectra of glasses in the system: (a) (100–x) GeS₂-xSb₂S₃; (b) Ge₁₂Sb_yS_88-y.

Fig. 2: Acoustic attenuation and acoustic velocity versus (a) Sb₂S₃content in (100–x) GeS₂-xSb₂S₃glasses; (b) Sb content in Ge₁₂Sb_yS_88-yglasses.

Table 1. Properties relating to acousto-optic figure of merit at 1550 nm