Fig. 1. Structure diagram of Pr³⁺ energy level^[13]

Fig. 2. Schematic diagram of the laser experimental setup^[15]

Fig. 3. Schematic diagram of welding of ZBLAN fiber. (a) Schematic diagram of welding; (b) micrograph of welding point^[18]

Fig. 4. Experimental setup of Q-switched pulsed laser oscillation^[31]

Fig. 5. Schematic diagram of Tb³⁺energy level^[33]

Fig. 6. Output characteristics and spectrum of Tb³⁺∶fluoride fiber laser^[37]

Fig. 7. Schematic diagram of pumping of Tb³⁺ doped fluoride fiber ^[10]

Fig. 8. Schematic diagram of Dy³⁺energy level^[13]

Fig. 9. Performance of Dy∶ZBLAN fiber. (a) Slope efficiency; (b) laser spectrum; (c) intensity distribution; (d) curve of laser center wavelength versus pump power and output power versus time^[43]

Fig. 10. Schematic diagram of the Ho³⁺ energy level^[33]

Fig. 11. Tunable laser output spectrum of Ho³⁺ doped ZBLAN fiber laser^[50]

Fig. 12. Schematic diagram of 532 nm green light pumping Ho³⁺ to realize 750 nm laser energy level^[53]

Fig. 13. Performance of Ho³⁺ doped ZBLAN fiber pumped by 532 nm laser. (a) Output power; (b) laser spectrum; (c) intensity distribution of laser spot; (d) variation curve of laser output power with time^[53]

Fig. 14. Variation curve of 319 nm laser output power with InGaN-LD injection power^[62]

Fig. 15. Schematic diagram of the frequency-doubling deep-ultraviolet laser device^[63]

Fig. 16. Performance of frequency-doubled deep-ultraviolet laser. (a) Spectrum; (b) output power and slope efficiency^[63]