Ca3Ga2Ge3O12 Garnet Claddings for YAG Fiber Lasers

This is the authors' abstract. We don't add key points for this paper.

The feasibility of cladding single-crystal YAG fibers with melted Ca3Ga2Ge3O12 garnet (CGGG), with a melting point of 1370–1385 °C, was investigated. CGGG was melted and crystallized on single-crystal Y3Al5O12 (YAG) plates and fibers at controlled temperatures and heating/cooling rates. CGGG precursors were coextruded with single-crystal YAG fibers, melted, and crystallized using a travelling furnace, and using laser heated pedestal growth (LHPG). Single-crystal YAG fibers were also dip-coated with molten CGGG. The CGGG microstructures were characterized by optical microscopy, SEM, electron back-scatter diffraction, and TEM. In experiments with YAG plates, chemically induced grain boundary migration was observed at the CGGG-YAG interface. The CGGG viscosity was too low to apply thick claddings by dip coating in melt or by use of a traveling furnace, but this was not an issue for the LHPG based method. For cladding applied by LHPG,a ~ 1–2 μm thick layer intermediate in composition between CGGG and YAG was observed. All the CGGG claddings were polycrystalline, regardless of the method used; none were epitaxial with YAG. Cladding microstructures and the merit of the various cladding methods are discussed.