Power Scaling of Narrow-Linewidth Fiber Amplifier Seeded by Yb-Doped Random Fiber Laser

In this paper, we propose and experimentally demonstrate a 2.4-kW narrow-linewidth amplifier seeded by a random fiber laser (RFL) with Yb-doped fiber gain. The high power lasing is realized by employing a master oscillator power amplifier (MOPA) configuration, a full width at half-maximum linewidth of 0.23 nm and a beam quality of M 2 = 1.28 are obtained at the maximum output. Theoretical models for the spectral evolution in high-power fiber amplifiers seeded by RFL are also proposed. It is found that spectral broadening exists in high-power MOPA using RFL as the seed. Meanwhile, spectral broadening can be further suppressed by employing active fiber with shorter length or larger core diameter. The theoretical predictions are in qualitative agreements with the experimental results.