We report on the first laser operation of a novel double molybdate compound, Yb:KY(MoO4)2. Single-crystals were grown by the Low Temperature Gradient (LTG) Czochralski method. The crystal structure (orthorhombic, sp. gr. Pbna – D142h) 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 (100) plane. The stimulated-emission cross-section for Yb3+ ions is 3.70×10-20 cm2 at 1008.0 nm and the emission bandwidth is 37 nm (for light polarization E ||b). Continuous-wave laser operation is achieved in a 3 at.% 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 linear polarization. Yb:KY(MoO4)2 crystal films / plates are attractive for sub-ns passively Q-switched microchip lasers and thin-disk lasers.
We report on fabrication, structure, spectroscopic and nonlinear properties of a new functional optical material – transparent glass-ceramics (GCs) based on Co2+,Ga3+-codoped ZnO (Co2+:GZO) nanocrystals. The introduction of Ga3+ cations that are smaller than Zn2+ ones and have a different valence state, is expected to modify the crystal field around the Co2+ ions leading to broadband absorption at the 4A2(4F) → 4T1(4F) transition. The glass of the ZnO – K2O – Al2O3 – SiO2 system was doped with 3 mol% Ga2O3 and 0.05 mol% CoO. Transparent GCs were produced by secondary heattreatments at 680 – 860 °C. They contained one crystalline phase - nanosized (8 – 26 nm) hexagonal GZO crystals, Ga3+ ions being distributed between the ZnO nanocrystals and the residual glass. The absorption spectra of GCs contained an intense band at 1.3-1.65 μm related to the 4A2(4F) → 4T1(4F) Co2+ transition in Td sites. A rise of IR losses due to the free charge carrier scattering in GZO was observed. Absorption saturation of transparent GCs was studied at ~1.54 μm. They exhibited low saturation fluence, 0.7–1.3 ± 0.2 J/cm2, and high laser-induced damage threshold, ~25 J/cm2. Co2+,Ga3+- codoped ZnO-based transparent GCs are promising for passive Q-switching of eye-safe erbium lasers emitting at ~1.5- 1.7 μm.