Fig. 1. Schematic diagram of fluoride fiber laser device. (a) Experimental setup of 30.5 W all-fiber laser operating at 2.94 µm^[13]; (b) experimental setup of 41.6 W fluoride fiber laser operating at 2.82 µm^[14]

Fig. 2. Fabrication process of chalcogenide fiber micro-FBG^[31]. (a) Schematic diagram of grating fabrication device; (b) typical optical micrograph of imaging system during grating fabrication process; (c) optical microscope image and (d) SEM image of chalcogenide micro-FBG with diameter of 2.4 µm

Fig. 3. Grating structures fabricated in chalcogenide glass bulk and fiber by femtosecond laser direct writing^[32]

Fig. 4. Schematic diagram of LPFG fabrication by mechanical stress device^[36]

Fig. 5. Microscopic images of passive three-core tellurite FBG structures^[39]. (a) Top view; (b) side view

Fig. 6. Structure of 3.55 µm all-fiber laser^[50]

Fig. 7. Schematic diagram of 3.55 µm gain-switched fiber laser^[51]

Fig. 8. 3.34 μm cascaded Raman laser based on As₂S₃ fiber and relationship between average laser output power and pump power^[65]

Fig. 9. 3.77 μm cascaded Raman fiber laser device based on As₂S₃ fiber grating^[34]

Fig. 10. Schematic diagram of (a) first-order and (b) second-order Raman tellurite fiber lasers^[71]

Fig. 11. LPFG stress sensor^［76］. (a) Experimental setup; (b) transmission spectrum