Epitaxial Growth of NaGd_0.935Yb_0.065(WO₄)₂ Layers on Lattice Matched Tetragonal Double Tungstate Substrates for Ultrafast Thin Disk Lasers

Liquid-phase epitaxial growth of Yb 3+ doped NaGd(WO 4 ) 2 crystalline layers has been obtained on Y modified NaGd(WO 4 ) 2 Czochralski grown single crystal substrates. It is shown that the lattice parameter of the layer and substrate can be equalized by proper selection of the Yb and Y compositions. The epitaxial layers obtained are highly transparent, with thicknesses in the range 10−70 μm, and with crystallographic quality close to that of the used substrates. The spectroscopic properties of Yb 3+ in the layer are anisotropic and similar to those of Yb-doped NaGd(WO 4 ) 2 single crystals. The layers are envisaged as optical gain media for the design of ultrafast mode-locked thin disk lasers.