High-Power 1120-nm Yb-Doped Fiber Laser and Amplifier

An all-fiberized, laser-diode-pumped, high-power, 1120-nm Yb-doped fiber laser with master oscillator power amplifier configuration was demonstrated. The seed was a 178-W single-mode fiber laser with an optical efficiency of nearly 70%. An amplifier stage was built to boost the power to 309 W with the slope efficiency of 80%. The M² factors, measured in the end of the amplifier at output power of 253 W, are 2.45 and 2.82 in x- and y-directions, respectively. A numerical model was also proposed to evaluate the ability of seed power level in suppressing amplified spontaneous emission in the fiber amplifier. The result indicates that the ratio of the pump power and seed power should not be higher than four for our amplifier if there is no special design to suppress amplified spontaneous emission.