150 mW unsaturated output power at 3 μm from a single-mode-fiber erbium cascade laser

We report on an erbium cascade laser in a fluorozirconate fiber. Lasing on the transition 4I11/2→4I13/2 at 2.71 μm is supported by colasing on the transition 4S3/2→4I9/2 at 1.72 μm. This recycles the excitation that is lost via excited-state absorption and avoids the saturation of the output power. Threshold at 2.71 μm is 33 mW launched pump power at 791 nm. The measured slope efficiency of 22.6% is relatively close to the 29.1% stokes-efficiency limit. An output power of 158 mW is obtained, limited only by the 1.43 W power available from the Ti: sapphire pump laser. Output power is 15 and slope efficiency 2.5 times higher than reported in previous publications.