Fig. 1. Ytterbium-doped polarization-maintaining fiber. (a) Optical fiber cross section; (b) refractive index profile

Fig. 2. Test device diagram of birefringence coefficient

Fig. 3. Spectrum of PM-YDF beat length

Fig. 4. Structural diagram of all polarization maintaining fiber laser based on oscillator structure

Fig. 5. Experimental results. (a) Output power of 11 µm/125 µm PM-YDF versus pump power; (b) output power of PLMA-YDF-10/125-M versus pump power; (c) output spectrum of 11 µm/125 µm PM-YDF when laser power is 12 W; (d) output spectrum of 11 µm/125 µm PM-YDF when laser power is 48.9 W