Abstract

The output energy and range of the pump power of a flash lamp pumped pulsed Cr:Tm:Ho:YAG laser is limited by thermal phenomena. As was shown in Ref. ¹, with increasing pump power from a given value, the output energy and efficiency decreased till the generation broke off. This effect, caused by a temperature increase in the laser rod, can be explained alternatively by the increase of population of lower laser level belonging to the ground level multiplet or by increase of diffraction losses due to thermal focusing. It was shown that for practical cases [see Refs. 1 and 2], the thermal relaxation constant was about 1 s for YAG rods, so in the case of pulse repetition frequency >5 Hz the temperature gradients in the rods are stationary. Due to lower transfer efficiency and higher threshold in comparison to Nd:YAG, thermal focusing in Ho:YAG is much stronger. The main aim of our work was to investigate dependencies of divergence and beam quality of Ho:YAG laser on pump power.

© 1994 IEEE