Fig. 1. DSC spectra of 80GeS₂·20Ga₂S₃+xEr (GG-xEr, x=0, 0.25, 0.5, 0.75, 1, 1.25) chalcogenide glass samples

Fig. 2. Transmission spectrum. (a) 80GeS₂·20Ga₂S₃+xEr (GG-xEr, x=0, 0.25, 0.5, 0.75, 1, 1.25) chalcogenide glass; (b) glass-ceramic after crystallization at 450 °C for 5 h (inset: sample photo)

Fig. 3. XRD pattern. (a) 80GeS₂·20Ga₂S₃+xEr (GG-xEr, x=0, 0.25, 0.5, 0.75, 1, 1.25) chalcogenide glass; (b) glass-ceramic sample after crystallization treatment at 450 ℃ for 5 h

Fig. 4. FESEM images. (a) GG-0Er chalcogenide glass; (b) glass-ceramic samples after crystallization treatment at 450 ℃ for 5 h

Fig. 5. Up-conversion spectra under excitation at 1550 nm. (a) GG-xEr chalcogenide glass; (b) glass-ceramic sample after crystallization treatment at 450 °C for 5 h; (c) luminescence intensity at 980 nm as a function of Er ion doping mole fraction