Fig. 1. Structure of (a) GaF₃-based and (b) InF₃-based glasses^[27]

Fig. 2. (a) Raman spectroscopy under different temperatures, the insets in the figure are the [InF₆]³⁻ vibration units; (b) The ratio of integral areas of δF_nb and SSF_nb^[30]

Fig. 3. (a) DSC and (b) refractive index dispersion of fluoroindate glasses

Fig. 4. (a) Simplified energy level diagram of Dy³⁺ ions and (b) experimental schematic of fiber laser^[40]

Fig. 5. (a) Diagram of the ~2.9 μm fiber laser setup and (b) diagram of pump power as a function of output power

Fig. 6. (a) Energy level diagram of the Ho³⁺: InF₃ system with relevant physical processes; (b) Experimental setup of the room-temperature fiber laser at 3.92 μm^[45]