Fig. 1. Thermal effects in fiber laser oscillator

Fig. 2. Thermal effects in MOPA configuration

Fig. 3. Beam spats before mode instability threshold(a) and after the system reached mode instability threshold(b)^[25]

Fig. 4. Different kinds of fiber colling groove structures^[44]

Fig. 5. 20 kW laser output of local LMA-48/400-YDF fiber by 1018 nm-tandem-pumping^[8]

Fig. 6. F-layer assisted triple-clad laser fiber

Fig. 7. High-power laser system using F-layer-assisted triple-clad fiber^[49]

Fig. 8. 10kW-level side pumping technique of IPG company, USA^[56]

Fig. 9. Configuration of GTwave cascaded fiber oscillator^[72]

Fig. 10. (8+1) Pump gain Integrated Functional Laser (PIFL) fiber: (a) end cross-section; (b) pump-coupling method^[5-6]

Fig. 11. (8+1) PIFL fiber laser: (a) output signal power and optical-to-optical efficiency; (b) laser beam spectrum^[5-6]

Fig. 12. 10 kW-level PIFL fiber laser configuration^[5-6]

Fig. 13. (a) absorption evolution; (b) temperature distribution of core region and polymer clad along PIFL fiber^[71]

Fig. 14. (8+1) PIFL oscillator structure^[76]