Fig. 1. Structural diagram of 2 kW-level fiber laser system reported in 2005^[16]

Fig. 2. Structural diagram of 10 kW-level single-mode fiber laser^[33]

Fig. 3. Development data of diode laser in recent years from homepages of nlight Inc. and IPG Inc. (a) Brightness increment data; (b) cost decrement data

Fig. 4. Structural diagram of 4 kW narrow linewidth fiber laser based on tandem pumping scheme^[64]

Fig. 5. Structural diagram of 5 kW output power system enabled by power amplification scheme ^[121]

Fig. 6. Covering ranges of gain-spectra of three typical doped fibers^[33]

Fig. 7. Output power scaling of high power Raman laser

Fig. 8. Mid-infrared fiber laser with > 40 W output power^[219]. (a) Structural diagram; (b) experimental result

Fig. 9. Structural diagram of 550 W-level all-fiberized single-frequency laser^[254]

Fig. 10. 16-lasers coherent beam combining system^[292]. (a) Structural diagram; (b) spectrum at maximal output power

Fig. 11. Tunable fiber laser with nearly kilo-nanometer tuning range^[310]. (a) Spectra; (b) output power characteristics

Fig. 12. Output characteristics of mode-tunable fiber laser from nlight Inc.^[323] .(a) Output spot patterns; (b) transmission parameters and diameters of different spots