Temporally stretched Q-switched pulses in the 2μm spectral range

A Q-switched Ho:YAG laser, longitudinally in-band pumped by a thulium fiber laser at a wavelength of λ = 1920 nm was designed in order to temporally stretch the Q-switched pulses at the fundamental wavelength. This was realized by two different methods: (a) wavelengths with a small cross section for stimulated emission have been selected, which leads to a pulse duration of 162 ns at 2128 nm compared to 32 ns at a wavelength of 2098 nm with energies around 1 mJ, (b) additionally intracavity second harmonic generation in the overcoupling regime has been used to further increase the pulse duration up to 300 ns at 1 mJ.