Abstract

Intense, ultrafast laser systems with an emission wavelength at around 2 µm have become popular tools for many scientific research activities such as nonlinear frequency conversion into the long-wave mid-infrared [1] as well as the soft X-ray spectral region [2], in order to address numerous subsequent applications. There is, however, a strong application-driven demand for an increase in photon-flux, i.e. repetition rate and average power, of the driving laser systems. Thulium-doped fiber lasers are an average-power scalable laser concept at around 2 µm emission wavelength. They have been demonstrated with >100 W average power and show great promise to deliver peak powers of several tens of GW [3, 4]. Another advantage is the large gain bandwidth offered by Tm-doped fused silica, spanning from 1.8-2 µm [5].

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