2 x 3 kW bidirectional output fiber oscillator employing spindle-shaped ytterbium-doped fiber

A 2 x 3 kW-level bidirectional output fiber oscillator is realized by combining the specially designed spindle-shaped ytterbium-doped fiber, non-wavelength-stabilized 976-nm LDs, and grating bandwidth optimization to balance transverse mode instability and stimulated Raman scattering. The maximum output powers at both ends are 3265 and 2840 W, respectively, with a total efficiency of 73.2%. The M 2 factors of the lasers at both ends are about 1.98 and 2.38, respectively. The beam profile at both ends shows that a bidirectional output annular beam fiber oscillator has been realized, which has great potential in practical applications.