Mapping subcycle electron motion by modulated high-order harmonic generation

Abstract

We theoretically investigate high-order harmonic generation in argon gas driven by two orthogonally polarized laser pulses of single color, with the consideration of the macroscopic propagation effect including fundamental and harmonic fields. Both the three-dimensional propagation simulation and a simple analytical model based on a single-atom level demonstrate that the harmonic intensity of any harmonic order varies periodically when the delay between two pulses is scanned. This significant intensity modulation provides an experimentally observable contrast, from which the electron excursion time of a short quantum path associated with a certain harmonic order can be directly read. The result shows that the attosecond time-resolved electron motion can be mapped onto the macroscopic harmonic intensity modulation