Growth, spectroscopy, and laser characterization of Er:KGdxYbyY1-x-y(WO4)2 epitaxial layers.

We report on the composition of Er-doped KGdxYbyY1-x-y(WO4)2 layers to be grown onto undoped KY(WO4)2 substrate providing fine lattice matching and high refractive index contrast with the substrate and fabrication of high optical quality Er(1.3 at. %):KGd0.2Yb0.15Y0.65(WO4)2 epitaxial layers with thickness up to 180 µm. Absorption and luminescence properties of the layer were measured and laser action under direct in-band pumping was reported for the first time, to our knowledge, in a non-waveguide configuration. A maximum output power of 16 mW with slope efficiency of 64% was achieved at 1606 nm.