MODIFIED BRIDGMAN GROWTH OF ORIENTED ER-DOPED AND TM-DOPED BAY2-XYBXF8 CRYSTALS FOR UP-CONVERSION VISIBLE LASER OPERATION

High-quality, oriented crystals of BaY1.5Yb0.49Er0.0lF8 have been grow n under hydrogen fluoride from BaYYbF8 seed crystals by a gradient-fre eze, stationary-solidification modification of the vertical Bridgman m ethod. Emission spectra obtained parallel and perpendicularto [010] sh ow marked anisotropy. The room-temperature upconversion laser threshol d for the 4F9/2-4I15/2 transition at 670 nm (with 960-nm pumping from a titanium:sapphire laser) with the output propagating perpendicular t o [010] is approximately two thirds that when propagating parallel to [010], consistent with the differences observed in fluorescence emissi on spectra obtained for the two polarizations.