Erbium:Ytterbium codoped large-core fiber laser with 297-W continuous-wave output power

We have demonstrated a high-power and high-efficiency erbium:ytterbium (Er:Yb) codoped fiber laser that produces 297 W of continuous-wave output at 1567 mn. The slope efficiency with respect to the launched pump power changed from 40 % to 19 % at higher output power due to the onset of Yb colasing at 1067 mn. However, the Yb colasing was essential for the suppression of catastrophic pulsation at high pump powers that otherwise results if the Yb-band gain is allowed to build up. Spectroscopic characteristics of the fiber and the impact of the Yb colasing on the 1567-nm slope efficiency are also discussed.