Thermo-optical modeling of high power operation of 2 μm codoped Tm,Ho solid-state lasers

The results of coupled thermo-optical modeling of Tm,Ho solid-state laser operation are reported. A rate dynamics model integrated together with a TEM00 distribution for the total number of stimulated photons is coupled with a two-dimensional time-dependent heat transfer model. The heat transfer model includes absorption, heat release, and transfer inside the crystal as well as the thermal effect of the spontaneously emitted infrared radiation. In water cooled crystal operation this radiation is shown to be absorbed within the water boundary layer, producing significant inhibition of dissipation of the heat released inside the crystal. This effect leads to crystal superheating and significant inhibition of laser energy output. Absorption loss, in particular, due to water vapor present in the cavity is found to decrease significantly laser pulse energy. Numerical results are compared to previous (Tm,Ho:yttrium lithium fluoride) and new (Tm,Ho:ceramic yttrium aluminum garnet) experimental data and discussed...