Abstract
Crystals of and grown by the gradient-freeze method under a hydrogen fluoride atmosphere operate as lasers at 348, 456, 482, 512, and 649 nm when upconversion pumped at 960 nm. The 649-nm red lasers show a clear orientation dependence; lasing is observed only when propagation is perpendicular to the crystallographic [010] direction. The orientation dependence of the red fluorescence confirms that the laser transition is exclusively polarized parallel to [010]. Ellipsoidal representations of intensities are determined from fluorescence data for several red and blue transitions. A crystal with composition is considered as representative of the upconversion laser media. Stark levels for the and states are determined from absorption and fluorescence over a range of temperatures from 10 to 298 K. A Judd–Ofelt analysis that averages data for three orthogonal polarizations is also performed.
© 1998 Optical Society of America
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