# Joule-level high effiency energy transfer to sub-picosecond laser pulses by a plasma-based amplifier

## TL;DR

This paper demonstrates laser plasma amplification of sub-picosecond pulses exceeding one Joule with up to 20% efficiency, advancing the development of ultra-high intensity laser systems.

## Contribution

It provides the first experimental demonstration of Joule-level, high-efficiency plasma-based amplification of sub-picosecond laser pulses and offers detailed simulations matching experimental results.

## Key findings

- Achieved up to 20% energy transfer efficiency.
- Identified a minimum seed intensity for effective amplification.
- Observed seed energy losses due to spontaneous backward Raman scattering.

## Abstract

Laser plasma amplification of sub-picosecond pulses above the Joule level is demonstrated, a major milestone for this scheme to become a solution for the next-generation of ultra-high intensity lasers. By exploring over 6 orders of magnitude the influence of the incident seed intensity on Brillouin laser amplification, we reveal the importance of a minimum intensity to ensure an early onset of the self-similar regime, and a large energy transfer with a very high efficiency, up to 20%. Evidence of energy losses of the seed by spontaneous backward Raman is found at high amplification. The first three-dimensional envelope simulations of the sub-picosecond amplification were performed, supplemented by one-dimensional PIC simulations. Comparisons with the experimental results demonstrate the capability of quantitative predictions on the transferred energy. The global behavior of the amplification process, is reproduced, including the evolution of the spatial profile of the amplified seed.