The far-field temporal information of ultrashort ultra-intense lasers at focus is crucial for strong-field physics research. However, current far-field characterization mainly relies on reconstruction from near-field data combined with a transfer function, and the associated error can exceed 50%. To address this problem, we propose a direct diagnostic method for the far field of a laser based on a plasma grating. The temporal information of the laser pulse is encoded into the plasma grating through interference-driven ionization and is then reconstructed from the diffraction of a probe beam, thereby enabling direct measurement of the laser temporal properties in the focal region.Experimentally, we demonstrate for the first time the measurement of far-field temporal information at a peak intensity of about . The pulse duration is measured over the range from 35 to 130 fs. Within a 100 ps temporal window, the dynamic range of the temporal contrast reaches , with a resolution better than 100 fs.This method features a simple experimental setup, no restriction on the laser central wavelength, and reliable operation at extremely high peak intensities. It therefore provides a robust solution for far-field diagnostics in high-power laser systems.
 

Plasma grating,Far-Field,Ultrafast Measurement