Characterization of bubble core and cloudiness in [Yb.super. 3+]:[Sr.sub.5][[(P[O.sub.4]).sub.3]F crystals using micro-Raman spectroscopy

Micro-Raman spectroscopy is used to characterize two common growth-induced defects, including bubble core and cloudiness in ytterbium doped strontium fluoroapatite [Yb.sup.3+]:[Sr.sub.5][(P[O.sub.4]).sub.3]F (Yb:S-FAP) crystals. Several types of impurities are identified that are distributed randomly in the cloudy region, thus leading to improvement of Y-SFAP quality and its optical application.