3.15 kW direct diode-pumped near diffraction-limited all-fiber-integrated fiber laser

We demonstrate a direct diode-pumped all-fiber-integrated fiber laser based on master oscillator power amplifier configuration at 1080 nm, producing maximum output power of 3.15 kW with corresponding optical to optical efficiency of 75.1%. Further power scaling is pump-limited and theoretical analysis demonstrates that 4 kW output power can be further achieved without stimulated Raman scattering. Near diffraction-limited beam quality (M-2 similar to 1.6 in the x and y directions) is also achieved at the maximum output power. This compact prototype laser has excellent stability and reliability, which could benefit many practical applications, such as industrial processing. (C) 2015 Optical Society of America