Abstract

The potassium double tungstates KY(WO₄)₂, KGd(WO₄)₂, and KLu(WO₄)₂ are recognized as excellent host materials for rare-earth-ion-doped lasers, see Ref. [1] and Refs. therein. Especially KY(WO₄)₂:Yb³⁺, hereafter abbreviated as KYW:Yb³⁺, exhibits large absorption and emission cross-sections, a small quantum defect [2], and laser emission with high slope efficiencies. Liquid phase epitaxy (LPE) has been used to grow thin layers of KYW:Yb³⁺ onto pure K Y W substrates and planar waveguide lasing with slope efficiencies up to 80% has been demonstrated in samples doped with 1.2-2.4% Yb³⁺ [3]. Recently, similar results have been obtained under diode pumping with a monolithic cavity [4]. The main disadvantage of this approach for fabricating integrated devices is the fact that the choice of rather low Yb^{3 +} concentration is governed by the need to optimize the laser properties, resulting in a low refractive-index contrast between layer and substrate of only a few ×10⁻⁴. This inhibits downscaling the waveguide thickness to 1-2 μm.

© 2009 IEEE