Effect of doping distribution on the lasing performance of a cerium-doped lithium calcium aluminum fluoride ultraviolet laser crystal

Abstract

We report multi-photon luminescence and Laser Ablation–Inductively Coupled Plasma Mass Spectrometry (LA-ICPMS) as a non-destructive and sensitive method of visualizing the concentration and distribution of activator ions doped to a crystal host, respectively. Here, LA-ICPMS is able to detect concentrations that are less than 0.1%. Using these methods and a large 110-mm diameter Czochralski method-grown cerium-doped lithium calcium aluminum fluoride (Ce3+:LiCaAlF6 or Ce:LiCAF), we observed that Ce is distributed non-uniformly with varying concentrations across the diameter of the crystal boule. We further verify quantitatively that luminescence intensity increases in proportion to doping density. Ultraviolet (UV, 290-nm wavelength) laser emissions from areas of the Ce:LiCAF crystal having different doping distributions and concentrations reveal that a uniform doping distribution leads to a higher slope efficiency, lower laser threshold and a potentially higher damage threshold even though the doping concentration is low compared to areas with high but non-uniform doping. Our results show a means of improving laser performance by aiming to achieve a uniform doping distribution; and multi-photon luminescence and LA-ICPMS are powerful tools that could aid in this process. Improved laser performance could lead to new breakthroughs in laser output energies especially in the UV region for many applications.