Investigations of a 439 W Narrow-Linewidth Er/Yb Fiber Amplifier Pumped by 1018 nm Fiber Lasers

In this paper, a 439 W, 1567 nm, narrow-linewidth Er/Yb co-doped fiber (EYDF) laser system pumped by 1018 nm fiber lasers is demonstrated. The 1018 nm fiber lasers are utilized as pumping source to suppress the ∼1 µm amplified spontaneous emission. It is the highest output power reported for EYDF lasers to date. A novel EYDF model considering the pair-induced quenching (PIQ) and the excited state absorption (ESA) of Er ions is built to predict the experiment more accurately. Simulation results reveal that ESA and PIQ both contribute to the decline of laser efficiency. Moreover, the scheme of the main amplifier is optimized theoretically based on the model to reach higher output power.