<title>Growth of Yb-doped fluorapatate crystal and study of its defects and spectroscopy performance</title>

Abstract

We have successfully grown Yb:FAP(fluorapatite) crystal doped with 1 - 5 at% Yb by CZ technique. Crystalline boules which are colorless and transparent have the size of 22 mm in diameter and 45 mm in length. The optimal growth parameters are presented. During a Yb:FAP crystal growth run there exists a continuous loss of fluoride through evaporation, so 5% excess of calcium fluoride was usually added. To eliminate the defects, a post-annealing method has been developed where the boule is suspended above the melt surface for two days in a temperature zone that is about 400 degrees Celsius below the melting point. The defects of crystals were discussed, and the spectroscopy performances of Yb:FAP crystal were reported.