Enhancing laser beam performance by interfering intense laser beamlets

A Morace,Y Sakawa,H Azechi,K Mima,Y Sentoku,S Lee,T Norimatsu,N Iwata,M Nakai,R Kodama,H Shiraga,Hiroaki Nishimura ,Junji Kawanaka ,Alexander A Andreev ,Kazuki Matsuo ,Noriaki Miyanaga ,S Tosaki,X Vaisseau,Yasunobu Arikawa ,Shigeki Tokita ,Sadaoki Kojima ,Akifumi Yogo ,Shinsuke Fujioka ,Masayuki Hata ,Shohei Sakata ,N Kamitsukasa,Yoshio Abe

doi:10.1038/s41467-019-10997-1

Abstract

Increasing the laser energy absorption into energetic particle beams represents a longstanding quest in intense laser-plasma physics. During the interaction with matter, part of the laser energy is converted into relativistic electron beams, which are the origin of secondary sources of energetic ions, γ-rays and neutrons. Here we experimentally demonstrate that using multiple coherent laser beamlets spatially and temporally overlapped, thus producing an interference pattern in the laser focus, significantly improves the laser energy conversion efficiency into hot electrons, compared to one beam with the same energy and nominal intensity as the four beamlets combined. Two-dimensional particle-in-cell simulations support the experimental results, suggesting that beamlet interference pattern induces a periodical shaping of the critical density, ultimately playing a key-role in enhancing the laser-to-electron energy conversion efficiency. This method is rather insensitive to laser pulse contrast and duration, making this approach robust and suitable to many existing facilities.

Highlights

Increasing the laser energy absorption into energetic particle beams represents a longstanding quest in intense laser-plasma physics
The recent development of multi-kJ and multi-PW laser systems typically coupled to large laser facilities represented a major step for high energy density (HED) physics research
These laser systems are devoted to the generation of bright particle and X-ray sources that find a myriad of applications in HED science, from isochoric heating of materials or dense plasmas to determine equations of state[1,2,3] to X-ray or proton radiography of HED plasmas[4,5] as well as generation of collisionless shocks for experimental astrophysics[6]

Summary

Introduction

Increasing the laser energy absorption into energetic particle beams represents a longstanding quest in intense laser-plasma physics. The simulations closely reproduce the experimental results with larger laser-to-electron and laser-to-ion energy conversion efficiency as well as higher hot electron slope temperature and peak proton energy for interfering beamlets compared to single beamlet irradiation as represented, f.

Results

Conclusion