Gain of electron orbital angular momentum in a direct laser acceleration process

Abstract

Three-dimensional "particle in cell" simulations show that a quasistatic magnetic field can be generated in a plasma irradiated by a linearly polarized Laguerre-Gauss beam with a nonzero orbital angular momentum (OAM). Perturbative analysis of the electron dynamics in the low intensity limit and detailed numerical analysis predict a laser to electrons OAM transfer. Plasma electrons gain angular velocity thanks to the dephasing process induced by the combined action of the ponderomotive force and the laser induced-radial oscillation. Similar to the "direct laser acceleration," where Gaussian laser beams transmit part of its axial momentum to electrons, Laguerre-Gaussian beams transfer a part of their orbital angular momentum to electrons through the dephasing process.

Optimizing direct laser-driven electron acceleration and energy gain at ELI-NP

“…It was also demonstrated that Laguerre-Gaussian beams transfer a part of their OAM to electrons through the dephasing process similar to the direct electron acceleration (DLA) in Gaussian beams [15]. Vacuum-based charge acceleration with Laguerre-Gaussian beams has also been studied very recently [16,17] showing that it is possible to generate GeV high-quality electron bunch with low spread in energy and radial deflection.…”

Kilo-Tesla axial magnetic field generation with high intensity spin and orbital angular momentum beams

“…Recent work has analyzed the motion of free electrons in a LG beam in more detail, expanding to first and second order perturbations [13,15]. It was shown that angular momentum can be transferred to free electrons in LP LG beams when considering second order terms in the equations of motion; the electron gains and loses angular momentum but averaging over one laser cycle yields zero net angular momentum transfer.…”

“…If the pulse is circularly polarized (CP) and of relativistic intensity, the generated magnetic field strength can be on the order of 100's of Tesla, last several picoseconds, and extend over millimeter scales [1]. The IFE has been studied extensively with CP beams both theoretically [2][3][4][5][6][7][8], and experimentally [1,9,10]; yet the effect is not exclusive to CP beams but also applicable to lasers carrying orbital angular momentum (OAM) [11][12][13]. Currently, we only know of one analytic model describing OAM driven magnetic fields and its transverse profile [11], but has not been verified numerically or experimentally.…”

“…Recent works have looked at simulating IFE driven * longman1@llnl.gov magnetic fields from OAM beams in various configurations: OAM beams with radial and azimuthal polarization [12], amplification of seeded magnetic fields [17], spatiotemporal light springs [18], and most recently linearly polarized OAM beams [13]. In these studies the laser intensities were of moderate intensity (I 0 ≈ 10 18 Wcm −2 ) verifying the existence of weaker magnetic fields (≈ 10 T), with little modelling of the spatial or temporal properties of the magnetic fields.…”

Direct Laser-Driven Electron Acceleration and Energy Gain in Helical Beams

“…It was also demonstrated that Laguerre-Gaussian beams transfer a part of their OAM to electrons through the dephasing process similar to the direct electron acceleration (DLA) in Gaussian beams [15]. Furthermore, the propagation of optical beams with OAM leads to plasma waves that may also carry OAM which couple to the plasma electrons and involve Landau damping and particle acceleration accompanied with the generation of quasi-static axial and azimuthal magnetic fields [16].…”