Spectrally resolved spatiotemporal features of quantum paths in high-order harmonic generation

TL;DR

This paper experimentally disentangles and maps the spectrally and spatially resolved quantum paths in high-order harmonic generation, revealing their physical mechanisms and enabling retrieval of atomic dipole phases and temporal chirps.

Contribution

It introduces a method to distinguish and analyze quantum paths in HHG through spectrally and spatially resolved measurements, advancing understanding of their physical mechanisms.

Findings

Spectral splitting and frequency shifts observed for quantum paths.

Quantum path interference affects harmonic yield modulation.

Atomic dipole phases are encoded in frequency shifts, enabling phase retrieval.

Abstract

We experimentally disentangle the contributions of different quantum paths in high-order harmonic generation (HHG) from the spectrally and spatially resolved harmonic spectra. By adjusting the laser intensity and focusing position, we simultaneously observe the spectrum splitting, frequency shift and intensity-dependent modulation of harmonic yields both for the short and long paths. Based on the simulations, we discriminate the physical mechanisms of the intensity-dependent modulation of HHG due to the quantum path interference and macroscopic interference effects. Moreover, it is shown that the atomic dipole phases of different quantum paths are encoded in the frequency shift. In turn, it enables us to retrieve the atomic dipole phases and the temporal chirps of different quantum paths from the measured harmonic spectra. This result gives an informative mapping of spatiotemporal and spectral features of quantum paths in HHG.