150 MW UNSATURATED OUTPUT POWER AT 3 MU-M FROM A SINGLE-MODE-FIBER ERBIUM CASCADE LASER

An output power of 158 mW at 2.71 μm from an erbium-doped single mode fluorozirconate-fiber cascade laser, working on transitions 4I11/2 → 4I13/2 and 4S3/2 → 4I9/2, was achieved. The threshold for the 2.71 μm transition was 33 mW with a slope efficiency of 22.6% in the cascade lasing regime. The output power was constrained by the pump power available from the Ti:sapphire laser. This represented the elimination of the saturation effect noted so far in the erbium 3 μm fiber laser and rendered this laser able to compete with the most effective erbium 3 μm crystal lasers.