Passively Q-switched Er:YAG laser operating at 1617 nm at low pump power level

We carried out an experimental study of an Er:YAG laser that is passively Q-switched by Cr:ZnSe saturable absorbers and pumped at 1470 nm by a 14 W laser diode. The 1617 nm emission is selected by an appropriate combination of transmissions of the saturable absorber and of the output coupler. With an accurate comparison between actively Q-switched and passively Q-switched operations and with Cr:ZnSe transmission measurements, we demonstrated by experiments and by simulations that the output energy is strongly dependent on the Cr:ZnSe temperature. With a better cooling of the Cr:ZnSe crystal heated by residual pump and signal absorption, the energy per pulse can be doubled, from 110 to 220 μJ, at a repetition rate of 800 Hz.