Crystal growth, characterization and thin disk laser operation of KLu1−xTmx(WO4)2/KLu(WO4)2 epitaxial layers

Abstract

Epitaxial samples of KLu_1−xTm_x(WO₄)₂/KLu(WO₄)₂ (x up to 0.15) have been obtained by the Liquid Phase Epitaxy (LPE) method. The lattice mismatch between the epitaxial layer and the substrate is small enough to allow the growth of good quality, well-oriented, single crystalline epilayers as evidenced by the 2θ scan of the (0k0) reflections and the rocking curve of the (040) reflection. Electron probe microanalysis shows an increase of 10²¹Tm³⁺ at cm⁻³ in a 2.5 μm interval at the substrate/layer interface. The main morphologies observed in the epilayers are steps and growth spirals. The laser operation around 2 μm, realized with epitaxial layers of 15 at% Tm doping and three different thicknesses, in a thin disk laser configuration with only two pump passes through the epitaxial layer, demonstrates maximum average output power as high as ∼1.4 W corresponding to a slope efficiency of 40%.