A Comparative Study of Continuous Wave Ti:Sapphire, Cr:LiSAF, Cr:LiCAF and Alexandrite Lasers in Thin-Disk Geometry

The thermo-opto-mechanical strength of Yb:YAG gain media has enabled average power scaling of solid state lasers to the multi-kilowatt regime in thin-disk (TD) geometry. However, the relatively narrow emission bandwidth of Yb:YAG is an important limitation, restricting obtainable pulsewidths and tunability. Hence, research for alternative broadband TD laser (TDL) materials with suitable thermo-opto-mechanical parameters has been an active field. Part of this effort is focused on other Yb+
³
-doped gain media; however, with their ultra broad emission bandwidths, transition-metal-doped laser media are other potentially attractive alternatives. In that respect, the recent TDL work with Ti:Sapphire is quite interesting [1]. However, due to its low gain product (product of fluorescence lifetime and emission cross section) and its susceptibility for nonradiative transitions at elevated temperatures, Ti:Sapphire poses many challenges for power scaling even in TD geometry, resulting in limited continuous-wave (cw) laser performance (~13% slope efficiency, 7.5 W output power using a 0.1% output coupler) [1]. Note that, due to the low gain of the system, the aforementioned performance is only possible with the usage of a high-quality factor cavity with minimal intracavity losses.