Low threshold laser-diode side-pumped Tm:YAG and Tm:Ho:YAG lasers

We report results from transverse laser-diode pumping of Tm:YAG and Tm:Ho:YAG rods. Using two 60-W quasicontinuous-wave laser-diode bars and a special dielectric coating structure on the barrel surface of the laser rod, laser operation was obtained at room temperature with threshold pump energies below 100 mJ and with output pulse energy above 10 mJ in free-running operation and 2 mJ in Q-switched operation. The Tm:Ho:YAG laser was more susceptible to a temperature increase in the material and performed significantly poorer in the Q-switched mode of operation than the Tm:YAG laser. This was predicted by a model accounting for up conversion and the dynamic equilibrium between the upper levels in thulium and holmium in Tm:Ho:YAG.