Soft x-ray high order harmonic generation driven by high repetition rate ultrafast thulium-doped fiber lasers

Martin Gebhardt; Tobias Heuermann; Ziyao Wang; Mathias Lenski; Christian Gaida; Robert Klas; Alexander Kirsche; Steffen Hädrich; Jan Rothhardt; Jens Limpert

doi:10.1117/12.2546151

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21 February 2020 Soft x-ray high order harmonic generation driven by high repetition rate ultrafast thulium-doped fiber lasers

Martin Gebhardt, Tobias Heuermann, Ziyao Wang, Mathias Lenski, Christian Gaida, Robert Klas, Alexander Kirsche, Steffen Hädrich, Jan Rothhardt, Jens Limpert

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Proceedings Volume 11260, Fiber Lasers XVII: Technology and Systems; 112600U (2020) https://doi.org/10.1117/12.2546151
Event: SPIE LASE, 2020, San Francisco, California, United States

Abstract

Intense, ultrafast laser sources with an emission wavelength beyond the well-established near-IR are important tools for exploiting the wavelength scaling laws of strong-field, light-matter interactions. In particular, such laser systems enable high photon energy cut-off HHG up to, and even beyond, the water window thus enabling a plethora of subsequent experiments. Ultrafast thulium-doped fiber laser systems (providing a broad amplification bandwidth in the 2 μm wavelength region) represent a promising, average-power scalable laser concept in this regard. These lasers already deliver ~100 fs pulses with multi-GW peak power at hundreds of kHz repetition rate. In this work, we show that combining ultrafast thulium-doped fiber CPA systems with hollow-core fiber based nonlinear pulse compression is a promising approach to realize high photon energy cut-off HHG drivers. Herein, we show that thulium-doped, fiber-laser-driven HHG in argon can access the highly interesting spectral region around 90 eV. Additionally, we show the first water window high-order harmonic generation experiment driven by a high repetition rate, thulium-doped fiber laser system. In this proof of principle demonstration, a photon energy cut-off of approximately 400 eV has been achieved, together with a photon flux <10⁵ ph/s/eV at 300 eV. These results emphasize the great potential of exploiting the HHG wavelength scaling laws with 2 μm fiber laser technology. Improvements of the HHG efficiency, the overall HHG yield and further laser performance enhancements will be the subject of our future work.

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Martin Gebhardt, Tobias Heuermann, Ziyao Wang, Mathias Lenski, Christian Gaida, Robert Klas, Alexander Kirsche, Steffen Hädrich, Jan Rothhardt, and Jens Limpert "Soft x-ray high order harmonic generation driven by high repetition rate ultrafast thulium-doped fiber lasers", Proc. SPIE 11260, Fiber Lasers XVII: Technology and Systems, 112600U (21 February 2020); https://doi.org/10.1117/12.2546151

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