Abstract

Planar optical devices play an increasingly important role as the components for fiberoptic communication systems. Liquid phase epitaxy (LPE) is a suitable technique to produce diode laser pumped solid state laser with a planar waveguide structure. Among several solid state laser hosts, the rare-earth doped YAG is a most promising candidate for diode-pumped waveguide lasers. In particular rare earth doped YAG epitaxial layers on YAG substrate have been demonstrated to have excellent laser properties. The realization of garnet active waveguides on YAG substrate requires an increase of refractive index between thin layer and substrate by an amount of 10^–2. The substitution of aluminum by gallium in YAG leads to increase of refractive index. Gallium has larger ionic radius than aluminum, so substitution of Al³⁺ by Ga³⁺ in YAG increase also lattice constant. Thus, it is necessary to adjust the lattice mismatch by co-doping with a small non optical active rare earth ion like lutetium in yttrium sites.

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