A power scaling strategy for longitudinally diode-pumped Tm:YLF lasers

We describe a power scaling strategy for longitudinally diode-pumped Tm:YLF lasers based on optimisation of the thulium doping level and the gain geometry. Carefully designed laser experiments at lower powers are shown to allow a simple means for accurately predicting the thermal loading and hence the power scaling properties of this system, including the effects of ground-state depletion, cross-relaxation and energy transfer upconversion. An optimised doping level of 2at.% and a slab geometry are shown experimentally to allow scaling of a single gain unit to output powers of ~70W, limited by the available pump power, and a strategy for scaling well beyond 100W output is discussed