All-optical spatio-temporal metrology for isolated attosecond pulses

TL;DR

This paper introduces an all-optical method for complete spatio-temporal characterization of isolated attosecond pulses, overcoming previous limitations of temporal-only measurements and revealing weak spatio-temporal couplings.

Contribution

The authors develop a novel FROG-like retrieval technique to measure the full space-time electric field of IAPs using spatio-spectral modulations induced by a non-collinear perturbing pulse.

Findings

Successfully reconstructed the spatio-temporal structure of IAPs in near- and far-field.

Revealed weak spatio-temporal coupling in IAP generation.

Demonstrated the method's ability to overcome limitations of traditional temporal-only schemes.

Abstract

Characterizing an isolated attosecond pulse (IAP) is essential for its potential applications. A complete characterization of an IAP ultimately requires the determination of its electric field in both time and space domains. However, previous methods, like the widely-used RABBITT and attosecond streaking, only measure the temporal profile of the attosecond pulse. Here we demonstrate an all-optical method for the measurement of the space-time properties of an IAP. By introducing a non-collinear perturbing pulse to the driving field, the process of IAP generation is modified both spatially and temporally, manifesting as a spatial and a frequency modulation in the harmonic spectrum. By using a FROG-like retrieval method, the spatio-spectral phases of the harmonic spectrum are faithfully extracted from the induced spatio-spectral modulations, which allows a thoroughgoing characterization of the IAP in both time and space. With this method, the spatio-temporal structures of the IAP generated in a two-color driving field in both the near- and far-field are fully reconstructed, from which a weak spatio-temporal coupling in the IAP generation is revealed. Our approach overcomes the limitation in the temporal measurement in conventional in situ scheme, providing a reliable and holistic metrology for IAP characterization.