Single-shot in situ pulse-duration measurement using plasma grating

TL;DR

This paper introduces a plasma grating-based single-shot diagnostic for in situ measurement of ultrashort laser pulse durations at focus, overcoming damage thresholds and spatial averaging issues of traditional methods.

Contribution

The authors develop a novel plasma grating technique that encodes pulse duration in its axial length and retrieves it via Bragg diffraction, enabling accurate in situ measurements.

Findings

Effective pulse-duration measurement over 35-130 fs range.

Method remains effective at peak intensities of ~10^16 W/cm^2.

Potential extension to 15-300 fs and higher intensities.

Abstract

Accurate measurement of the pulse duration of ultrashort, ultra-intense laser pulses at focus is essential for strong-field science. Most existing diagnostics, however, cannot allow direct in situ measurement in the focal region because of damage-threshold limits and unavoidable spatial averaging. We present a direct single-shot far-field diagnostic based on a plasma grating. In this method, the pulse duration is encoded in the axial length of an interference-written plasma grating and retrieved from the corresponding Bragg-diffraction signal. Comparison with near-field (pre-focus) autocorrelator measurements and far-field (at-focus) scanning measurements confirms single-shot pulse-duration retrieval in the focal region over 35-130 fs, and the method remains effective at a peak intensity of $\sim 10^{16}{\rm W/cm^2}$. In principle, the measurable range can be extended to 15-300 fs and to higher peak intensities. The method is insensitive to the laser central wavelength and offers a practical approach to far-field diagnostics in high-power laser systems.