Abstract
We present a compact extreme ultraviolet (XUV) source based on high-harmonic generation (HHG) at 2.4 MHz pulse repetition rate driven from the compressed output of a mode-locked thin-disk laser (TDL) oscillator. The system generates very high peak intensities, which enable highly nonlinear frequency conversion reaching VUV/XUV energies. These sources significantly increase the signal-to-noise ratio and reduce measurement durations in many fields such as condensed matter physics. The pulse repetition rate is increased from kilohertz to megahertz with high average photon flux, while keeping the pulse energy sufficiently low to avoid space charge effects. The system uses a semiconductor saturable absorber mirror mode-locked Yb:YAG TDL delivering an average power of up to 70 W with subpicosecond pulses, which are efficiently compressed to sub-100 fs in a simple, single-stage compressor based on a Kagome-type hollow-core photonic crystal fiber. Focusing into a high-pressure xenon gas jet, we generate XUV radiation with up to >5×107 photons/s on the 19th harmonic (23 eV). This HHG system is very compact, has low-noise performance comparable to standard ultrafast low-power laser oscillators, and provides a new tool for the study of attosecond dynamics in condensed matter physics.
Highlights
Current femtosecond and attosecond pulses in the vacuum ultraviolet (VUV) to extreme ultraviolet (XUV) spectral regime, generated using high-harmonic generation (HHG) [1], typically have energies of 1–10 nJ at around 1 kHz repetition rate with pulses as short as ≈70 attoseconds (i.e., 1 as 10−18 s) [2]
We have proposed to bridge this gap by the development of novel high-average-power, high-pulse-energy femtosecond laser oscillators [4] and for the first time applied them to high-field physics experiments with photoelectron imaging spectroscopy using only 1 μJ pulse energy from a diode-pumped, ultrafast, solid-state laser oscillator at 14 MHz pulse repetition rate [5]
In this Letter, we use more than one order of magnitude more pulse energy to demonstrate for the first time, to the best of our knowledge, the applicability of these high-power lasers for HHG at few-megahertz pulse repetition rate
Summary
Current femtosecond and attosecond pulses in the vacuum ultraviolet (VUV) to extreme ultraviolet (XUV) spectral regime, generated using high-harmonic generation (HHG) [1], typically have energies of 1–10 nJ at around 1 kHz repetition rate with pulses as short as ≈70 attoseconds (i.e., 1 as 10−18 s) [2]. High-flux, high-repetition-rate, compact XUV sources based on HHG have seen enormous progress in the past decade, closely linked to recent record average powers achieved with ultrafast IR driving sources based on Yb-doped, diode-pumped, chirped pulse fiber laser amplifiers [10], innoslab amplifiers [11], thindisk multipass and regenerative amplifiers [12], and thin-disk oscillators [13,14] These sources reach impressive levels, even surpassing the kilowatt average power milestone, the peak powers available still remain moderate compared to Ti:Sapphire amplifiers, due to the longer pulse durations limited by the standard Yb-doped gain media. We believe this result is the first step towards the generation of compact XUV sources driven by tabletop oscillators, which would provide an outstanding low-noise, compact, and coherent XUV source
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
