Fig. 1. Mode bend loss dependent on the bend radius of the 30/600 μm Yb-doped fiber

Fig. 2. Ytterbium doped fiber output laser power. (a) Relationship between the output laser power and the Yb³⁺ doped fiber length; (b) variation of the dual-end pump power and the output laser power along the fiber when the Yb³⁺ doped fiber length is 19.2 m

Fig. 3. Experimental setup of the laser system

Fig. 4. Spectrum and beam quality of the seed laser. (a) Spectrum; (b) beam quality

Fig. 5. Output laser power and beam quality dependent on the bend radius of the Yb-doped fiber

Fig. 6. Laser power and slope efficiency measured

Fig. 7. Spectra and beam quality of the output signal laser. (a) Spectra; (b) beam quality

Fig. 8. Temperature measurements of the amplifier compositions when operating at the full laser power. (a) Yb-doped fiber temperature and temperature of the splicing point between the backward combiner and the doped fiber; (b) temperature of the output cladding light stripper; (c) temperature of the forward and backward combiners

Fig. 9. Measurement of the power stability during 90 s