Extreme–ultraviolet high–harmonic generation in liquids

Abstract

High–harmonic generation (HHG) in gases has been the main enabling technology of attosecond science since its discovery. Recently, HHG from solids has been demonstrated, opening a lively area of research. In contrast, harmonic generation from liquids has so far remained restricted to low harmonics in the visible regime. Here, we report the observation and detailed characterization of extreme ultraviolet HHG from liquid water and several alcohols extending beyond 20 eV. This advance was enabled by the implementation of the recent liquid flat–microjet technology, which we show to facilitate the spatial separation of HHG from the bulk liquid and the surrounding gas phase. We observe striking differences between the HHG spectra of water and several alcohols. A comparison with a strongly–driven few–band model establishes the sensitivity of HHG to the electronic structure of liquids. Our results suggest liquid–phase high–harmonic spectroscopy as a new method for studying the electronic structure and ultrafast scattering processes in liquids.

Cooperative evolution of intraband and interband excitations for high-harmonic generation in strained MoS2

“…Here, is the lattice constant, and are the n th Fourier coefficient of the Berry curvature and the lowest conduction band, respectively. In this semiclassical treatment, the dynamic evolution of the pre-existing wave-packet and the subsequently HHG emission are closely related to the magnitudes of and [2,55]. We emphasize that although the intuitive model using pure intraband dynamics can qualitatively capture the main features of HHG, it must be scrutinized when interband transitions also contribute to the generation process.…”

Orientation-dependent transition rule in high-order harmonic generation from solids

“…It has quickly expanded into other bulk and layer solid materials, and is realized in liquids recently [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19]. HHG from solids also provides a novel tool to investigate properties of the crystal materials, such as the reconstruction of the band structure and the Berry curvature [20][21][22][23]. Various physical mechanisms of HHG in solids have been introduced.…”

Probing the dephasing time of crystals via spectral properties of high-order harmonic generation

“…Attosecond pulses generated by gas-phase HHG provide a powerful tool for the probe of ultrafast dynamics in atoms, molecules, and biological systems [2][3][4][5]. Given the potential as a bright, compact, controllable source of extreme ultraviolet radiation and the promise of applying HHG spectroscopic techniques to correlated quasiparticle dynamics in condensed matter [6,7], the realization of efficient HHG from transparent crystals has inspired enormous interests [8][9][10][11][12][13][14][15] and been demonstrated as an alternative way to study properties of the bulk materials, such as the reconstruction of the energy bands and the Berry curvature [16][17][18][19][20][21].…”