Probing Spatiotemporal Reshaping of Three-Color Laser Waveforms in a Gas Medium via High-Order Harmonic Generation Spectroscopy

The spatiotemporal properties of a multicolor laser waveform during its propagation in a gas medium are of great interest, but they cannot be obtained using traditional characterization methods for ultrashort laser pulses. In this work, we demonstrate that high-order harmonic generation (HHG) spectroscopy provides an opportunity to obtain this information. To this end, we first show that the experimentally measured HHG spectra of Ne atoms, generated using a long-duration three-color synthesizer in a long gas cell, can be reproduced by our simulation, and continuum harmonics appear in both experiment and simulation. By synthesizing an isolated attosecond pulse from the continuum harmonics, the spatiotemporal reshaping of the driving laser waveform can be explored. Next, by varying the time delay between two of the three colors, we extract the slope of the high-energy photons. In theory, our results demonstrate that the spatiotemporal reshaping of the three-color laser waveform can be identified through the relationship between the slope and the cutoff energy, with the single-atom response serving as a reference. This approach is anticipated to significantly expand the applications of multicolor lasers across diverse research fields.