550 mJ Q-switched cryogenic Ho:YLF oscillator pumped with a 100 W Tm:fiber laser

We report 550 mJ pulses with 14 ns FWHM duration at 1 Hz repetition rate from a Q-switched cryogenic Ho:YLF oscillator pumped with 100 W in 35 ms by a Tm:fiber laser. The laser has a confocal unstable resonator with a graded-reflectance output coupler, resulting in a beam quality of M(2) = 1.5. Pulse energies of 416 and 343 mJ were obtained at 10 and 20 Hz repetition rate, respectively.