High-power Er:YAG laser at 1646 nm pumped by an Er,Yb fiber laser

In this paper we describe an Er:YAG laser pumped by a tunable, cladding-pumped Er,Yb fiber laser and discuss factors affecting the laser performance. Crystals with different Er3+-concentrations in the range 0.5% to 4 at% and with crystal lengths selected for similar to95% absorption of the pump light at 1532 nm were used, and the laser performance was investigated for a range of output coupler transmissions (2-30%) at 1646 nm. In preliminary experiments we have achieved a maximum output power of 4W at 1646 nm for 11W of absorbed pump power corresponding to an efficiency of 36%, using a crystal with 0.5at% Er3+-concentration and an output coupler transmission of 10%. Our experiments have revealed that the cw efficiency decreases quite markedly for higher Er3+-concentrations. The origin this behaviour is currently the subject of a detailed experimental investigation and our preliminary findings will be presented. The prospects for further increase in output power and efficiency will also be discussed.