Efficient tunable laser operation of diode-pumped Yb,Tm:KY(WO4)2 around 1.9 μm

A new laser medium - Yb,Tm:KY(WO4)(2) - for diode pumped solid state laser applications operating around 1.9 to 2.0 mum has been investigated and the main laser characteristics are presented. Diode pumping at 981 nm and around 805 nm was realised. For 981-nm pumping, the excitation occurs into Yb3+ ions followed by an energy transfer to Tm3+ ions. A slope efficiency of 19% was realised. For pumping around 805 nm, the excitation occurs directly into the Tm3+ ions. Here a maximum slope efficiency of 52%, an optical efficiency of 40%, and output powers of more than 1 W were realised. Using a birefringent quartz plate as an intracavity tuning element, the tunability of the Yb,Tm:KY(WO4)(2) laser in the spectral range of 1.85-2.0 mum has been demonstrated. The possibility of laser operation in a microchip cavity configuration for this material has also been shown.