Waveform Control of Relativistic Electron Dynamics in Laser-Plasma Acceleration

Julius Huijts,Igor A Andriyash,Aline Vernier,Zhao Cheng,Jérôme Faure,Rodrigo Lopez-Martens,Lucas Rovige,Marie Ouillé,Jaismeen Kaur

doi:10.1103/physrevx.12.011036

Abstract

The interaction of ultraintense laser pulses with an underdense plasma is used in laser-plasma acceleration to create compact sources of ultrashort pulses of relativistic electrons and x rays. The accelerating structure is a plasma wave, or wakefield, that is excited by the laser ponderomotive force, a force that is usually assumed to depend solely on the laser envelope and not on its exact waveform. Here, we use near-single-cycle laser pulses with a controlled carrier-envelope phase to show that the actual waveform of the laser field has a clear impact on the plasma response. The beam pointing of our relativistic electron beam oscillates in phase with the carrier-envelope phase of the laser, at an amplitude of 15 mrad, or 30% of the beam divergence. Numerical simulations explain this observation through asymmetries in the injection and acceleration of the electron beam, which are locked to the carrier-envelope phase. These results imply that we achieve waveform control of relativistic electron dynamics. Our results pave the way to high-precision, subcycle control of electron injection in plasma accelerators, enabling the production of attosecond relativistic electron bunches and x rays.Received 26 May 2021Revised 10 December 2021Accepted 11 January 2022DOI:https://doi.org/10.1103/PhysRevX.12.011036Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI.Published by the American Physical SocietyPhysics Subject Headings (PhySH)Research AreasHigh intensity laser-plasma interactionsLaser wakefield accelerationPonderomotive effectsUltrashort pulsesAccelerators & BeamsPlasma PhysicsAtomic, Molecular & Optical

Highlights

Waveform control has revolutionized several domains of laser-matter interaction, as it allows for an extremely high degree of control on electron dynamics
First applied in the frequency domain to drastically improve atomic clock precision [1], it was quickly adopted by the strong-field physics community to control electron dynamics in photoionization [2] and high-harmonic generation in gases [3,4] as well as laser-induced fragmentation of molecules [5]
Theory and simulation studies show that the precise control of the laser waveform through the carrier-envelope phase (CEP) can have a strong impact in laser-plasma accelerator (LPA)

Summary

INTRODUCTION

Waveform control has revolutionized several domains of laser-matter interaction, as it allows for an extremely high degree of control on electron dynamics. Waveform control in laser-plasma interaction has been more difficult to achieve, because it requires few-cycle laser pulses with a stabilized carrier-envelope phase (CEP) [6] at intensities higher by several orders of magnitude. While most LPAs are driven by laser pulses containing many optical cycles, few-cycle pulses can be used to excite wakefields and accelerate electrons [20,21,22,23] In this case, the usual framework of a cycle-averaged ponderomotive force [24] is not sufficient to describe the interaction. Theory and simulation studies show that the precise control of the laser waveform through the CEP can have a strong impact in LPAs. Simulations indicate that singlecycle laser pulses cause significant asymmetries of the plasma wakefield [13,25].

EXPERIMENT

SIMULATIONS AND DISCUSSION

Findings

CONCLUSION AND OUTLOOK