High-order harmonic generation at a megahertz-level repetition rate directly driven by an ytterbium-doped-fiber chirped-pulse amplification system

Abstract

We report the first experimental demonstration (to our knowledge) of high-order harmonic generation in rare gases driven by a state-of-the-art high-power Yb-doped-fiber chirped-pulse amplification system. The fiber laser delivers 270 fs pulses in the 30-100 microJ energy range at repetition rates varying from 100 kHz to 1 MHz. A proper focalization allows reaching several 10(13) W/cm2 in a gas jet. We have been able to produce and detect harmonics up to order 31 (33.2 nm) in Ar at a 100 kHz repetition rate. High-order harmonic generation at 1 MHz is also demonstrated in Xe up to harmonic 15. The demonstrated extreme UV (XUV) source will bring ultrashort XUV coincidence experiments from synchrotron facilities to tabletop laboratories.

Exploring new avenues in high repetition rate table-top coherent extreme ultraviolet sources

“…All of these architectures are based on ytterbium-doped laser materials that limit the attainable pulse duration to a few hundred femtoseconds. Nevertheless, early experiments on HHG with fiber lasers have already indicated the great potential of these sources 16,17 , which has also been validated by the recently measured photon flux of 4.5 3 10 12 photons s -1 over several harmonics at 100 kHz repetition rate 18 . However, as noted above, the rather long pulse duration hinders efficient HHG, suggesting the need for post-compression techniques, such as nonlinear compression in noble gas-filled glass capillaries 19 .…”

Génération d’harmoniques d’ordres élevés à ultra haute cadence

“…Ces conditions de génération nous ont permis d'observer l'émission de radiations XUV et d'observer clairement que ces radiations étaient constituées d'harmoniques d'ordres élevés du fondamental [5]. Ceci est illustré sur la figure 3 qui représente le signal XUV détecté pour un taux de répétition de 100 kHz et pour une énergie par impulsion de 80 J (puissance moyenne 8 W).…”

“…Nous avons donc pu montrer qu'il est maintenant possible de générer des harmoniques d'ordres élevés à des cadences aussi haute que 1 MHz [5] ce qui n'avait auparavant jamais été fait avec un système laser amplifié. De plus, nous avons pu montrer qu'il est possible d'adapter le taux de répétition du système et le gaz utilisé pour générer une harmonique donnée jusqu'à l'ordre maximum de 31.…”

Optimized XUV source at 100 kHz repetition rate

“…The moderate energy and long duration of the pulses delivered by to these systems require tight focusing geometry leading to a reduced harmonic efficiency. Nevertheless, few groups reported the observation of high-order harmonics at very high repetition rate in such geometry [3][4][5]. In first experiment, HHG at repetition rates of up to one MHz has been reported using a 1030 nm fibre chirped-pulse amplification (FCPA) system [3].…”

“…Nevertheless, few groups reported the observation of high-order harmonics at very high repetition rate in such geometry [3][4][5]. In first experiment, HHG at repetition rates of up to one MHz has been reported using a 1030 nm fibre chirped-pulse amplification (FCPA) system [3]. By considering a 10 -6 typical conversion efficiency, 3×10 11 photons/s/harmonic has been estimated.…”