Fig. 1. Polarization ellipses of LP₀₁ and LP₁₁ modes at pump power of 0, 6.3, 12.3 W^[25]

Fig. 2. Spherical distance of two polarization states and the polarization evolution of LP₀₁ and LP₁₁ modes on the Poincaré sphere^[25]. (a) Polarization evolution of LP₀₁ and LP₁₁ modes on the Poincaré sphere; (b) spherical distance of two polarization states on the Poincaré sphere

Fig. 3. Calculated bending loss curves of LP₀₁ and LP₁₁ modes^[38]

Fig. 4. Under different output power, beam patterns before and after bending mode selection^[38]. (a) Before bending mode selection, at 570 W; (b) after bending mode selection, at 1.3 kW

Fig. 5. Bending loss curves of polarization modes^[39]

Fig. 6. Structure diagram of chirally-coupled-core fiber with multiple satellite cores^[48]

Fig. 7. Schematic diagram of chirally-coupled-core fiber with single satellite core^[49]

Fig. 8. Schematic diagram of refractive index profile and cross section of single trench fiber^[45]

Fig. 9. Structure diagram of confined-doping fiber^[52]

Fig. 10. Simulation of thermal depolarization of two pumping schemes under different pumping powers^[31]. (a) 3 kW; (b) 5 kW

Fig. 11. Experiment setup diagram of counter-tandem-pumping linearly polarized fiber laser^[60]

Fig. 12. 3.96 kW bidirectional pumping linearly polarized fiber laser^[65]

Fig. 13. Structure and refractive index distribution of triple-clad fiber^[56]

Fig. 14. Structure diagram of triple-clad fiber^[73]

Fig. 15. Experimental setup of 3.1 kW triple-clad linearly polarized fiber laser^[73]

Fig. 16. Flow chart of active polarization control^[35]

Fig. 17. 1.43 kW linearly polarized fiber laser based on active polarization control^[74]

Fig. 18. Active polarization control system of non-polarization maintaining fiber laser based on SPGD algorithm^[24]

Fig. 19. S/P-polarized laser power and PER versus total laser power^[24]

Fig. 20. Active polarization control system of non-polarization maintaining fiber laser based on RMS-prop algorithm^[20]