Spectroscopy and efficient laser operation of cleaving Yb: KY(MoO4)2 crystal

We report on the first laser operation of ytterbium-doped potassium yttrium double molybdate crystal (Yb:KY(MoO4)2). Single-crystals containing 3 at.% Yb3+-ions were grown by the low temperature gradient Czochralski method. The crystal structure (orthorhombic, sp. gr. D142h - Pbna) was refined with the Rietveld method. Yb:KY(MoO4)2 exhibits a layered structure leading to a strong optical anisotropy and a perfect cleavage along the crystallographic (100) plane. The maximum stimulated-emission cross-section amounts to 3.70×10-20 cm2 at 1008.0 nm with an emission bandwidth of 37 nm (for light polarization E || b). The Stark splitting is determined at 6 K. Continuous-wave laser operation is achieved in a thin Yb:KY(MoO4)2 crystal plate (thickness: 286 μm) under diode pumping. The microchip laser generated a maximum output power of 0.81 W at 1021-1044 nm with a slope efficiency of 76.4% and polarized emission. Yb:KY(MoO4)2 crystal lamellae / plates are attractive for sub-ns passively Q-switched microchip lasers and thin-disk lasers.