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Properties of Ce:LiSrAlF6 and Ce:LiCaAlF6 ultraviolet lasers

The ultraviolet laser properties of LiSrAlF6 doped with trivalent cerium (Ce:LiSAF) and LiCaAlF6 (Ce:LiCAF) are reported. The polarized absorption, emission and excited state absorption cross sections for both Ce:LiSAF and Ce:LiCAF were determined for the 266 nm pump and 290 nm laser emission wavelengths. The single exponential emission lifetime was measured to be 28 +/- 2 and 25 +/- 2 ns for Ce:LiSAF and Ce:LiCAF, respectively. The gain was found to be highest when the probe was polarized parallel to the optic axis of the crystal due to the anisotropic nature of the excited state absorption. The excited state absorption is ascribed to a transition from the 5d orbital of Ce3+ to the conduction band of the host. Laser slope efficiencies of up to 29% and 21% were measured for Ce:LiSAF and Ce:LiCAF when the 266 nm pulsed pump beam was polarized parallel to the optic or c- axis. These are the highest laser slope efficiencies yet observed for any known solid-state ultraviolet laser material. When the pump beam was polarized perpendicular to the optic axis of the crystals, the gain and laser efficiencies dropped by up to an order of magnitude. The magnitude of pump-induced solarization was found to be highly variable for different crystals, and to have insignificant impact on the laser performance when favorable crystals were utilized.