Influence of temperature dependent excited state absorption on a broadly tunable UV Ce:LiLuF laser

We report the experimentally measured polarized small signal gain for Ce:LiLuF at 309 run and 327 nm. The gain was found to be anisotropic and temperature dependent. Using a rate equation based model we have simulated the affect of excited-state absorption (ESA) on the small signal gain in Ce:LiLuF. As a result we report the polarized emission and ESA cross-sections for Ce:LiLuF at 309 nm and 327 nm. We show the ESA to be temperature dependent and consequently demonstrate that ESA is the cause of the change in small signal gain with temperature in Ce:LiLuF. Further, we experimentally show the decrease, with temperature, of the ESA cross-sections at 309 nm causes a 70% increase in the laser output at 309 nm. We demonstrate how the introduction of a σ-biased loss into the cavity suppresses σ-polarized lasing at 327nm. This counteracts the decrease in laser output below ∼10°C caused by the anisotropic nature and temperature dependence of the ESA in Ce:LiLuF at 327 nm.