Watt-level erbium-doped all-fiber laser at 3.44 μm.

We demonstrate a 3.44 μm all-fiber laser emitting a maximum of 1.5 W at room temperature, the highest continuous power ever generated from a mid-IR fiber oscillator clearly beyond 3 μm. The laser operates on the 4F(9/2)→4I(9/2) transition of erbium-doped fluoride glasses and relies on a dual pumping scheme at 974 and 1976 nm. By combining a dichroic mirror deposited on the input fiber tip and a fiber Bragg grating as an output coupler, a stable laser emission is produced with a FWHM bandwidth of less than 0.6 nm. The laser cavity has an efficiency of 19% with respect to the launched pump power at 1976 nm and no saturation is observed provided 974 nm co-pumping is sufficient. The joint effect of the two pumps is also investigated.