High-Flux synchrotron alternatives driven by powerful long-wavelength fiber lasers
Lasers, and in particular ultrafast lasers, are an enabling technology for many applications, with the particularity that they can emit high-powers and are tabletop at the same time. These characteristics have made intense laser radiation widely available, which has decisively contributed to the advancement of many fields. However, the spectral coverage of lasers is limited and, thus, there are many applications that can only be addressed with other sources such as synchrotrons. Unfortunately, synchrotrons have two strong disadvantages: they are very large facilities with restricted user access and are extremely expensive. This is seriously hampering the widespread use of this radiation and, with it, the progress and development of many fields.   Since a direct (i.e. a laser-based), high-power emission of coherent light with a wavelength coverage comparable to that of a synchrotron is impossible, nonlinear frequency conversion driven by a high-power solid-state laser seems to be the most elegant solution to achieve a high photon flux in important spectral regions such as the mid-infrared, the THz- and the soft-X-ray range. Most remarkably, frequency conversion into these spectral regions would strongly benefit from a longer driving laser wavelength than the standard Titanium:Sapphire or Ytterbium-based near-infrared emission. On top of that, the shift of the emission to longer wavelengths can unleash a hidden performance scaling potential of ultrafast fiber lasers, as nonlinear and thermal limitations scale favorably.  The goals of the project SALT are twofold. First, it targets a revolution in the performance level of ultrafast lasers by unlocking the potential of Thulium-doped fiber lasers. Second, it aims at demonstrating new realms of flux in selected wavelength regions by frequency-converting these high-power 2µm sources. This will pave the way for frontier applications allowing for seminal discoveries and breakthroughs.