A narrow bandwidth extreme ultra-violet light source for time- and angle-resolved photoemission spectroscopy

Abstract

Here we present a high repetition rate, narrow band-width, extreme ultraviolet (XUV) photon source for time-and angle-resolved photoemission spectroscopy (tr-ARPES). The narrow band width pulses ∆E = 9, 14, 18 meV for photon energies hν = 10.8, 18.1, 25.3 eV are generated through High Harmonic Generation (HHG) using ultra-violet (UV) drive pulses with relatively long pulse lengths (461 fs). The HHG setup employs an annuluar drive beam in a tight focusing geometry at a repetition rate of 250 kHz. Photon energy selection is provided by a series of selectable multilayer bandpass mirrors and thin film filters, thus avoiding any time broadening introduced by single grating monochromators. A two stage optical-parametric amplifier provides < 100 fs tunable pump pulses from 0.65 µm to 9 µm. The narrow bandwidth performance of the light source is demonstrated through ARPES measurements on a series of quantum materials including the high-temperature superconductor Bi-2212, WSe 2 and graphene.

Multispectral time-resolved energy-momentum microscopy using high-harmonic extreme ultraviolet radiation

“…Over the past fifteen years, trARPES has evolved into a powerful ARPES modality providing direct dynamical information on electronic structure at the fundamental time scales of electronic and atomic motion, particularly on photoinduced transient changes of electronic states and their population. [23][24][25][26][27][28][29][30][31][32] trARPES is now routinely performed using table-top laser sources based on fourth and higher harmonic generation (HHG) in solids 33,34 and gases [35][36][37][38][39][40][41][42][43][44][45][46][47][48][49][50] , respectively, as well as using free-electron lasers (FELs) based on the self-amplification of spontaneous emission (SASE) of free electrons in undulators. 21 The corresponding probe photon energies in trARPES range from the far UV to soft x-rays where a sweet spot currently is the intermediate extreme ultraviolet (XUV) regime.…”

“…In the XUV, HHG-based trARPES can optionally provide high time, energy, and momentum resolution in conjunction with kHz-to-MHz repetition rates and a sufficiently wide detection window of the surface-parallel momentum (k x , k y ) to fully cover typical Brillouin-zone (BZ) dimensions. [35][36][37][38][39][40][41][42][43][44][45][46][47][48][49][50] Moreover, HHG sources combined with monochromators enable multispectral measurements as they can deliver a useable, discretely tunable photon-energy range of ≈8-40 eV. 35,36,40,43,44,46 However, this multispectral capability has so far rarely been exploited in trARPES experiments, and recently several setups for HHG-based trARPES have even been optimized for operation at one specific photon energy only.…”

Ultrafast polarization-tunable monochromatic extreme ultraviolet source at high-repetition-rate

“…While some of these characteristics are individually reached in many HHG-based trARPES setups (e.g. see [44][45][46][47][48][49][50][51][52][53][54][55][56]), we are not aware of any light source delivering all these performance simultaneously. This represents a challenge that the current work aims at overcoming.…”