XUV Sources Based on Intra-Oscillator High Harmonic Generation With Thin-Disk Lasers: Current Status and Prospects

Abstract

Ultrafast thin-disk laser (TDL) oscillators provide higher intracavity pulse energy, average power, and peak power levels than any other femtosecond laser oscillator technology. They are suitable for driving extreme nonlinear interactions directly inside the laser oscillator. High harmonic generation (HHG) driven inside ultrafast TDL oscillators is a very recent approach for the generation of coherent extreme ultraviolet (XUV) light at multimegahertz repetition rates. In this paper, we review the current state of the development, discuss the technological potential, and give an outlook toward the future developments. We compare the current performance to established technologies and evaluate possible limitations. We discuss future improvements, such as reduction of the driving pulse duration and increase of the intracavity peak power, efficient extraction of the XUV light from the cavity, and carrier-envelope offset frequency stabilization of the generated XUV light. Due to the power scalability of the TDL concept and the possibility to operate in a spectrally broadened regime with pulse durations below the gain bandwidth limitation, intra-oscillator HHG with TDLs has a high potential for powerful table-top multi-megahertz coherent XUV light sources for science and applications.

Intra-oscillator high harmonic source reaching 100-eV photon energy

“…The approach has held a promise that it can tolerate higher cavity losses thanks to the presence of gain inside the cavity and that the free-running soliton can better adapt to the nonlinearities induced by the plasma in the gas target. Thus, it should be capable of providing higher HHG efficiencies through tolerating higher intensities in the gas target as well as allowing higher XUV outcoupling efficiencies [24]. In this study, we show for the first time that this promise of the intra-oscillator HHG approach can be honored.…”

“…The dashed connecting line shows the progress of the system developed in our laboratory. The underlying data has been obtained from [2,5,24,32,33].…”

Opening a new route to multiport coherent XUV sources via intracavity high-order harmonic generation

“…We conclude from the measured pulse duration and pulse energy that the peak power of the intracavity pulse reaches 0.87 GW. This is equivalent to ten-fold the magnitude of the highest intracavity average power ever obtained from a mode-locked oscillator developed for intracavity HHG 3 , 17 , 25 .…”

“…However, the repetition rate of the HH pulse, limited by the repetition rate of the fundamental laser system 3 , is still insufficient for novel applications, such as ultrafast XUV spectroscopy 4 , photoelectron spectroscopy 5 , and coincidence measurements using a velocity map imaging detector 6 or a reaction microscope 7 . In particular, an exceedingly high photon flux is necessary for implementing time-resolved high-precision photoemission spectroscopy, while the pulse energy should be lower than the threshold to induce the space charge effect, which distorts the photoelectron spectrum.…”

Attosecond spectroscopy for filming the ultrafast movies of atoms, molecules and solids

“…Another way to achieve high average power is to employ cavity-enhanced HHG, which can increase the repetition rate to tens of MHz with limited single-pulse energy. [47] 3. Pump-probe based attosecond spectroscopy Attosecond time-resolved techniques are developed on the basis of traditional femtosecond pump-probe schemes, in which the pump pulse and the probe pulse interact successively with matter to capture dynamic information, thus the whole process is a nonlinear process.…”