# Spatio-temporal structure of a Petawatt femtosecond laser beam

## TL;DR

This paper presents the first full spatio-temporal measurement of a PetaWatt femtosecond laser, demonstrating the effectiveness of existing techniques at extreme intensities and providing new insights into laser physics.

## Contribution

It introduces a complete spatio-temporal characterization method for PetaWatt lasers, confirming the suitability of CPA techniques at these high power levels.

## Key findings

- Successful full characterization of BELLA laser at full intensity
- CPA technique remains effective at PetaWatt scale
- Provides new insights into laser physics and operation regimes

## Abstract

The development of optical metrology suited to ultrafast lasers has played a key role in the progress of these light sources in the last few decades. Measurement techniques providing the complete $E$-field of ultrashort laser beams in both time and space are now being developed. Yet, they had so far not been applied to the most powerful ultrashort lasers, which reach the PetaWatt range by pushing the Chirped Pulse Amplification scheme to its present technical limits. This situation left doubts on their actual performance, and in particular on the peak intensity they can reach at focus. In this article we present the first complete spatio-temporal characterization of a PetaWatt femtosecond laser operating at full intensity, the BELLA laser, using two recently-developed independent measurement techniques. Our results demonstrate that, with adequate optimization, the CPA technique is still suitable at these extreme scales, i.e., it is not inherently limited by spatio-temporal couplings. We also show how these measurements provide unprecedented insight into the physics and operation regime of such laser systems.