Structural and Spectroscopic Characterization of Nominal Yb3+:Ca8La2(PO4)6O2 Oxyapatite Single Crystal Fibers Grown by the Micro-Pulling-Down Method

Yb-doped Ca8La2(PO4)6O2 (CLPA) single crystals with the apatite-type structure and having <0001> orientation were grown by the micro-pulling-down (μ-PD) method. The apatite structure is represented by the monophased field of Ca8(La2–xYbx)-(PO4)6O2 (CLYPA) where it is assumed that 2 Ca2+ sites are substituted by La3+ and Yb3+ cations. Its monophased range was found to be from x = 0.0 to 0.2. The segregation of Yb3+ in CLPA single crystals and the maximum Yb3+ concentration are discussed. The crystallinity was studied using X-ray rocking curve analysis. Absorption, emission and fluorescence decay studies of Yb3+ ions in CLPA were also carried out both at low temperature and room temperature. Spectroscopic data reveal Yb3+ ion occupation within different crystallographic sites of the apatite-type structure. The potential for a diode-pumped Yb3+ laser is evaluated.