Abstract
Absorption of angular momentum from a high intensity laser pulse can lead to the generation of strong axial magnetic fields in plasma. The effect, known as the inverse Faraday effect, can generate kilo-Tesla strength, multipicosecond, axial magnetic fields extending over hundreds of microns in underdense plasma. In this paper we explore the effect with ultrahigh intensity circularly polarized Gaussian beams and linearly polarized orbital angular momentum beams comparing analytic expressions with three-dimensional particle-in-cell simulations. We develop a model for the transverse magnetic field profiles, introduce a model for the temporal decay, and show that while the magnetic field strength is independent of plasma density, it has a strong dependence on the laser beam waist.
Highlights
The inverse Faraday effect (IFE) describes the generation of axial magnetic fields when angular momentum is transferred from a laser pulse to plasma
We explore the spatial and temporal scaling of IFE magnetic fields driven by ultrahigh intensity (I0 ≈ 1020 W cm−2) circularly polarized (CP) Gaussian and linearly polarized (LP) orbital angular momentum (OAM) beams
Taking the modulus squared of the field amplitude given in Eq (1) for | | 1, we find the so-called donut mode intensity profiles that are symmetric about the kz axis; the helical phase is lost in the modulus, resulting in no azimuthal structure in the intensity profile [14]
Summary
The inverse Faraday effect (IFE) describes the generation of axial magnetic fields when angular momentum is transferred from a laser pulse to plasma. Recent works have looked at simulating IFE driven magnetic fields from OAM beams in various configurations: OAM beams with radial and azimuthal polarizations [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 (I0 ≈ 1018 W cm−2), verifying the existence of weaker magnetic fields (≈10 T), with little modeling of the spatial or temporal properties of the magnetic fields.
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