Nonlinear magneto-optical response to light carrying orbital angular momentum

TL;DR

This paper predicts a significant nonlinear magneto-optical effect in magnetic insulators induced by intense light with orbital angular momentum, leading to large magnetic fields and controllable magnetization dynamics.

Contribution

It introduces a novel theoretical prediction of nonlinear magnetic field responses driven by OAM-carrying light in magnetic insulators, highlighting higher-order effects and their dependence on OAM.

Findings

Magnetic fields up to several Tesla can be generated by high-intensity OAM light.

The magnetic response includes second- and fourth-order contributions with opposite signs.

Changing the OAM direction controls the induced magnetic field orientation.

Abstract

We predict a non-thermal magneto-optical effect for magnetic insulators subject to intense light carrying orbital angular momentum (OAM). Using a classical approach to second harmonic generation in non-linear media with specific symmetry properties we predict a significant nonlinear contribution to the local magnetic field triggered by light with OAM. The resulting magnetic field originates from the displacement of electrons driven by the electrical field (with amplitude $E_0$) of the spatially inhomogeneous optical pulse, modeled here as a Laguerre-Gaussian beam carrying OAM. In particular, the symmetry properties of the irradiated magnet allow for magnetic field responses which are second-order ($\sim E_0^2$) and fourth-order ($\sim E_0^4$) in electric-field strength and have opposite signs. For sufficiently high laser intensities, terms $\sim E_0^4$ dominate and generate magnetic field strengths which can be as large as several Tesla. Moreover, changing the OAM of the laser beam is shown to determine the direction of the total light-induced magnetic field, which is further utilized to study theoretically the non-thermal magnetization dynamics.