In-Band Pumped Continuous-Wave Lasers Based on Ho:KY(WO4)2 Crystal and Ho:KGdYbY(WO4)2 Epitaxial Layer

2 mu m lasers are in demand for a number of practical applications, such as environmental monitoring, remote sensing, medicine, material processing, and are also used as a pump sources for optical parametric generators. Crystals of double potassium tungstates doped with ions of rare-earth elements were shown to be promising materials both for the creation of classical solid-state lasers and waveguide lasers. The aim of this work was to develop a tunable pump laser in the spectral region of 1.9 mu m based on double tungstate crystals doped with thulium ions and to study the lasing characteristics of a Ho:KY(WO4)(2) crystal and a Ho:KGdYbY(WO4)(2) single-crystal epitaxial layer under in-band pumping. With a Ho(1at.%):KY(WO4)(2) crystal, continuous wave low-threshold lasing with an output power of 85 mW with a slope efficiency of 54 % at 2074 nm was achieved. For the first time to our knowledge, continuous wave laser generation in a waveguide configuration is realized in a single-crystal layer of potassium tungstate doped with holmium ions grown by liquid-phase epitaxy. The maximum output power at a wavelength of 2055 nm was 16.5 mW.