Time-resolved momentum microscopy with a 1 MHz high-harmonic extreme ultraviolet beamline

Abstract

Recent progress in laser-based high-repetition rate extreme ultraviolet (EUV) lightsources and multidimensional photoelectron spectroscopy enable the build-up of a new generation of time-resolved photoemission experiments. Here, we present a setup for time-resolved momentum microscopy driven by a 1 MHz femtosecond EUV table-top light source optimized for the generation of 26.5 eV photons. The setup provides simultaneous access to the temporal evolution of the photoelectron´s kinetic energy and in-plane momentum. We discuss opportunities and limitations of our new experiment based on a series of static and time-resolved measurements on graphene.

Ultra-short-pulse high-average-power megahertz-repetition-rate coherent extreme-ultraviolet light source

“…1). An increase in XUV average power would help for example to mitigate space charge effects in photoelectron emission spectroscopy [17] (at high repetition rates), as well as to shorten acquisition times and, hence, enhance the signal-to-noise ratio in (time-resolved) coincidence measurements [18], XUVabsorption spectroscopy [19], XUV-ionization spectroscopy [20], coherent diffractive imaging of ultrafast magnetization dynamics [21], fluorescence spectroscopy [22] and XUV-pump XUV-probe experiments [23,24], among others. Furthermore, shortest pulses are desired to investigate fastest dynamics in atoms [6,25], molecules [26], ions [23], solids [19] and compound materials [27].…”

Biological Applications of Short Wavelength Microscopy Based on Compact, Laser-Produced Gas-Puff Plasma Source

“…Laser-plasma EUV sources for lithography are currently capable to obtain a flux of 10 8 photons/s [98], while ptychography sources enable a gain of 10 11 photons/s at 18 nm [99]. Recent progress pushed forward this limit, obtaining up to~2 × 10 12 photons/s with compact systems employing HHG [100].…”

The 2021 ultrafast spectroscopic probes of condensed matter roadmap

“…Similarly, time-resolved momentum microscopy setups were combined with ultrafast light sources in the EUV or soft x-ray range. This paved the way towards imaging ultrafast band structure renormalizations or the (excitonic) charge carrier dynamics in molecular and novel quantum materials in an exceptionally large range of momenta and throughout their entire surface BZ [115][116][117][118].…”

“…This approach, however, severely reduces the signal to noise ratio in the momentum microscopy data when reducing the average photon flux of the ultrafast light source at constant repetition rate. On the other hand, it can potentially result in a constant heating of the material when increasing the repetition rate of the ultrafast light source to compensate for the reduction of pump or probe photons per pulse [115]. This vicious circle can only be broken by novel innovative concepts for improving the momentum microscopy optics itself.…”