Magnetic field generation in plasma waves driven by co-propagating intense twisted lasers

TL;DR

This paper introduces a novel mechanism for generating strong, long-lasting magnetic fields in plasma using co-propagating twisted laser pulses with different frequencies and orbital angular momentum, confirmed by simulations and theory.

Contribution

The study demonstrates a new magnetic field generation method in plasma driven by the beating of twisted laser pulses with different OAM and frequencies, supported by theoretical and simulation results.

Findings

Magnetic fields up to 0.4 MG observed in simulations.

Long-lasting magnetic fields persist after laser passage.

New mechanism involves twisted ponderomotive forces and plasma waves.

Abstract

We present a new magnetic field generation mechanism in underdense plasmas driven by the beating of two, co-propagating, Laguerre-Gaussian (LG) orbital angular momentum (OAM) laser pulses with different frequencies and also different twist indices. The resulting twisted ponderomotive force drives up an electron plasma wave with a helical rotating structure. To second order, there is a nonlinear rotating current leading to the onset of an intense, static axial magnetic field, which persists over a long time in the plasma (ps scale) after the laser pulses have passed by. The results are confirmed in three-dimensional particle-in-cell simulations and also theoretical analysis. For the case of 300 fs duration, 3.8x10^17 W/cm^2 peak laser intensity we observe magnetic field of up to 0.4 MG. This new method of magnetic field creation may find applications in charged beam collimation and controlled fusion.