High-energy resonantly diode-pumped Q-switched Ho3+:YAG laser

We report on a Q-switched Ho 3 + :YAG laser resonantly pumped by fiber-coupled high-spectral-brightness laser diodes emitting at 1.91 μ m . Using a 75-mm-long composite crystal pumped by two fiber-coupled diode modules, 18 W was obtained at a wavelength of 2121 nm for 53 W of injected power with a slope efficiency of 51 % with respect to absorbed power. The beam propagation factor ( M 2 ) was measured to be 1.2 at the maximum output power. The laser performance in Q-switched operation was recorded for different repetition rates between 100 Hz and 20 kHz. A maximum output energy of 8.7 mJ was measured at 1 kHz repetition rate.