High Performance Ultrafast Thulium-Doped Fiber Lasers

Summary form only given. Ultrafast lasers that deliver intense femtosecond pulses at carrier wavelengths beyond the well-established emission bands of Yb- or Ti:Sa-based sources have become extremely popular drivers for scientific applications. It is widely known that the long wavelength is a key property to enable new strong-field experiments or to significantly improve existing ones, e.g. in the case of extreme nonlinear frequency conversion to otherwise hardly accessible spectral regions. Those spectral regions of interest range from the deep mid-infrared (based on parametric amplification in non-oxide crystals) up to the soft X-ray regime (via high-harmonic generation). In order to turn such laboratory experiments into real-world applications with improved signal-to-noise-ratios and fast data acquisition and to unlock applications within the industry sector as well, the long wavelength driving laser sources need to deliver high repetition rates and high average powers. Thulium-doped fiber laser systems represent a promising concept for the generation of energetic ultrashort pulses at around 2 gm wavelength with excellent average power handling capabilities. Making use of well -developed fused silica fi ber technology and the availability of commercial high -power pump laser sources, thulium -doped ultrafast fi ber lasers have reached a performance level that is no longer inferior to what ytterbium -doped fi ber laser systems deliver in the ultrafast regime. To date, these 2 gm fi ber laser systems can generate kW -class average power, or multi-GW peak power with only 100 fs pulse duration. In our contribution, we report on the current status of this laser technology and review its performance scaling prospects. Additionally, we discuss ultrafast thulium -doped fi ber laser systems as a power -scalable platform for few -cycle pulse generation at carrier wavelengths longer than 1 gm and we show application examples, which fundamentally benefit from the long wavelength.