Ytterbium calcium fluoride waveguide laser.

Calcium fluoride is a well-known material for optical components. It is also suited for doping with rare-earth ions, e.g., ytterbium ones. Yb:CaF is an efficient gain medium for high-power and ultrashort-pulse bulk lasers around 1 μm. We report on the first Yb:CaF planar waveguide laser. High-optical-quality single-crystalline waveguiding Yb:CaF thin films are grown on bulk CaF substrates by Liquid Phase Epitaxy. The spectroscopic study indicates the predominant coordination of isolated Yb ions in trigonal oxygen-assisted sites, C(T). The optical gain in Yb:CaF waveguide is demonstrated. A 1.4 at.% Yb:CaF planar waveguide laser generated 114 mW at 1037 nm with a slope efficiency of 12.9%. Yb:CaF films are promising for power-scalable waveguide mode-locked lasers and amplifiers.