Tuning time and energy resolution in time-resolved photoemission spectroscopy with nonlinear crystals

Abstract

Time- and angle-resolved photoemission spectroscopy is a powerful probe of electronic band structures out of equilibrium. Tuning time and energy resolution to suit a particular scientific question has become an increasingly important experimental consideration. Many instruments use cascaded frequency doubling in nonlinear crystals to generate the required ultraviolet probe pulses. We demonstrate how calculations clarify the relationship between laser bandwidth and nonlinear crystal thickness contributing to experimental resolutions and place intrinsic limits on the achievable time-bandwidth product. Experimentally, we tune time and energy resolution by varying the thickness of nonlinear β-BaB2O4 crystals for frequency upconversion, providing a flexible experiment design. We achieve time resolutions of 58–103 fs and corresponding energy resolutions of 55–27 meV. We propose a method to select crystal thickness based on desired experimental resolutions.

An Integrated Quantum Material Testbed with Multi-Resolution Photoemission Spectroscopy

“…0.1 µJ of the second harmonic (412 nm) and > 150 pJ of the fourth harmonic (206 nm) are obtained using BBO crystals built into the probe OPA. The pulse duration of the 206 nm beam varies between 27 and 115 fs, which is tuned by the thicknesses of the BBO crystals 25 . A prism-pair compressor compensates for the group velocity dispersion (GVD) and controls the bandwidth of the 206 nm beam.…”

“…This theoretical estimate is based on the analyzer resolution of 2 meV and the 6 eV laser bandwidth of 2.7 meV. 25 While it is difficult to characterize our momentum resolution, we present an upper limit by showing a momentum distribution curve (MDC) taken at the Dirac point of an antiferromagnetic topological insulator MnBi 2 Te 4 (Fig. 3(b)).…”

“…This integration brings fundamental challenges if using a single light source. For instance, the energy and temporal widths of light pulses are conjugate quantities dictated by the fundamental uncertainty principle 25 . A sub-100fs time resolution in trARPES is concomitant with an energy a) Electronic mail: yangsl@uchicago.edu resolution > 18 meV in static ARPES.…”

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

“…Over the past decades, there have been great improvements in synchrotron-based light sources which, together with new and more versatile electron analyzers, have pushed the energy and momentum-space resolutions in ARPES experiments to ever increasing levels 4,5 . In parallel to this development, ARPES has taken a leap into the time-domain due to the advent of femtosecond high-power lasers that have enabled ultrafast extreme-ultraviolet (XUV) light sources based on high-harmonic generation (HHG) in noble gases [6][7][8][9] or nonlinear crystals [10][11][12] . While several successful implementations of time-and angle-resolved photoemission spectroscopy (tr-ARPES) systems have been demonstrated, the technique continues to rapidly evolve and there is still much progress to be made in terms of increased repetition rate, photon flux, improved time and energy resolutions, photon energy and momentum range coverage as well as pump versatility.…”

Ultrafast time- and angle-resolved photoemission spectroscopy with widely tunable probe photon energy of 5.3-7.0 eV for investigating dynamics of three-dimensional materials

“…Timeand angle-resolved photoemission spectroscopy (TrARPES) [3,4] has been a powerful technique for capturing the ultrafast carrier dynamics and photo-induced phase transitions with energy-, momentum-and time-resolution. In the past decades, major progress has been made in TrARPES instrumentation, including extending the pump wavelength to midinfrared [5] or terahertz [6], improving the energy resolution or time resolution [7][8][9][10][11] etc. Developments in the probe source using high harmonic generation (HHG) [12][13][14], or free electron laser [15] with a higher probe photon energy have also been achieved.…”