A high-repetition rate attosecond light source for time-resolved coincidence spectroscopy

Abstract

Attosecond pulses, produced through high-order harmonic generation in gases, have been successfully used for observing ultrafast, subfemtosecond electron dynamics in atoms, molecules and solid state systems. Today’s typical attosecond sources, however, are often impaired by their low repetition rate and the resulting insufficient statistics, especially when the number of detectable events per shot is limited. This is the case for experiments, where several reaction products must be detected in coincidence, and for surface science applications where space charge effects compromise spectral and spatial resolution. In this work, we present an attosecond light source operating at 200 kHz, which opens up the exploration of phenomena previously inaccessible to attosecond interferometric and spectroscopic techniques. Key to our approach is the combination of a high-repetition rate, few-cycle laser source, a specially designed gas target for efficient high harmonic generation, a passively and actively stabilized pump-probe interferometer and an advanced 3D photoelectron/ion momentum detector. While most experiments in the field of attosecond science so far have been performed with either single attosecond pulses or long trains of pulses, we explore the hitherto mostly overlooked intermediate regime with short trains consisting of only a few attosecond pulses. We also present the first coincidence measurement of single-photon double-ionization of helium with full angular resolution, using an attosecond source. This opens up for future studies of the dynamic evolution of strongly correlated electrons.

High-Flux 100 kHz Attosecond Pulse Source Driven by a High-Average Power Annular Laser Beam

“…We make this distinction because temporal characterization is a demonstration of the attosecond pump-probe capability. As shown in Figure 1, single-pass HHG can provide high harmonics [17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36] up to tens of nJ per shot at 1 MHz by using powerful driving lasers with an average power up to ~100 W [37][38][39][40][41][42][43] and the attosecond pulses [44][45][46][47][48][49][50][51][52][53][54][55] up to hundreds of pJ per shot at 100 kHz. Intracavity HHG can deliver the high harmonics with the repetition rates up to hundreds of MHz [56][57][58][59][60][61][62][63].…”

Characterizing ultrashort laser pulses with second harmonic dispersion scans

“…Since its invention, the d-scan has become a well-established technique in many laboratories around the world. It has been implemented and tested with different target pulse widths and central frequencies, and d-scan-compressed pulses have enabled a variety of applications ranging from pump-probe spectroscopy to biomedical imaging [34][35][36][37].…”

High-flux 100-kHz attosecond pulse source driven by a high average power annular laser beam

“…Nowadays, more effort is put towards scaling up the flux using more powerful driving lasers with a repetition rate of ∼ 100 kHz and an average power of ∼ 100 W [6][7][8][9]. For the applications in which it is crucial to avoid space charge effects [10], and in time resolved coincidence measurements which require few events in each laser shot [11][12][13], in order to achieve a high signal-to-noise ratio, increasing both the repetition rate and the attosecond pulse energy are preferred. Furthermore, high repetition rate is beneficial in a wide range of experiments because the time necessary for data collection can be shortened.…”

“…For example, it will enhance the scope of single particle structural dynamics studies [14] by extending them to high harmonics based facilities. Thanks to the continuous development of laser technology, high repetition rate and high average power lasers have become available [7][8][9][15][16][17], and as a result there is a continuous increase in the achievable photon flux with attosecond sources [12,[18][19][20][21][22][23][24][25][26][27][28].…”