Attosecond soft X-ray high harmonic generation

Abstract

One contribution of 15 to a theme issue 'Measurement of ultrafast electronic and structural dynamics with X-rays' .High harmonic generation (HHG) of an intense laser pulse is a highly nonlinear optical phenomenon that provides the only proven source of tabletop attosecond pulses, and it is the key technology in attosecond science. Recent developments in highintensity infrared lasers have extended HHG beyond its traditional domain of the XUV spectral range (10-150 eV) into the soft X-ray regime (150 eV to 3 keV), allowing the compactness, stability and subfemtosecond duration of HHG to be combined with the atomic site specificity and electronic/structural sensitivity of X-ray spectroscopy. HHG in the soft X-ray spectral region has significant differences from HHG in the XUV, which necessitate new approaches to generating and characterizing attosecond pulses. Here, we examine the challenges and opportunities of soft X-ray HHG, and we use simulations to examine the optimal generating conditions for the development of high-flux, attosecond-duration pulses in the soft X-ray spectral range.This article is part of the theme issue 'Measurement of ultrafast electronic and structural dynamics with X-rays'.

The measurement of ultrafast electronic and structural dynamics with X-rays

“…It covers the broad features of each of the technologies, their current status and their potential future capabilities. Recent developments of sub-femtosecond HHG sources in the soft X-ray range are presented in the article by Johnson et al [19], where optimization of X-ray flux is discussed and possible scalings for future laser sources, e.g. at high repetition rate or with a higher power.…”

Dynamics of Ultrafast Phase Transitions in (001) Si on the Shock-Wave Front

“…Nowadays the time-resolved method that is applicable to the direct detection of phase transitions is limited by the time-resolved Raman scattering and X-ray diagnostics [17,18]. Recent progress in the generation of X-rays, both from free-electron lasers (FEL) and laser plasma, or from the high harmonic generation, which allows for the retrieval of the ultrafast dynamics of phase transitions [19][20][21]. Using such sources, the timeresolved experiments were successfully applied to the study of lattice dynamics [22,23], phase transitions [24,25], and phonon dynamics [26].…”

Synchronized beamline at FLASH2 based on high-order harmonic generation for two-color dynamics studies

“…15 In the last 20 years, ultrashort laser pulses have been routinely produced through high-order harmonic generation (HHG), [16][17][18][19][20] leading to important breakthroughs in the investigation of ultrafast electron dynamics in matter. [21][22][23][24] In a typical HHG setup, an ultraintense laser is focused (I > 10 14 W/cm 2 ) onto a gas-phase atomic target, triggering a strong-field photo-interaction: a valence electron is first ejected from the atom through tunneling, then accelerated by the external field, and eventually driven back to the parent ion. 25,26 The radiative electron recombination results in the emission of light bursts, with durations down to a few tens of attoseconds.…”