High power in-band pumped Er:YAG laser at 1617 nm

In this paper, we report the preliminary results for power scaling of an Er:YAG laser at 1617 nm in-band pumped by a high-power cladding-pumped Er,Yb fibre laser. In this preliminary study, a simple four-mirror folded cavity was employed for the Er:YAG laser comprising a 29 mm long Er:YAG rod with 0.5 at.% Er³⁺ concentration mounted in a water-cooled aluminium heat-sink, a plane pump in-coupling mirror with high reflectivity at 1617 nm and high transmission at 1532 nm, two concave mirrors of 100 mm radius of curvature and high reflectivity at 1617 nm, a plane output coupler of transmission, 30% at 1617 nm, and a 100 mum thick fused silica etalon. The Er:YAG laser yielded a maximum output power of 23 W for 68 W of pump power from the Er,Yb fibre laser. The threshold pump power was 1.9 W and the slope efficiency with respect to incident pump power was 38%. To the best of our knowledge, this result represents the highest output power so far demonstrated from an Er:YAG laser at 1617 nm.