Inverse-Faraday effect from the orbital angular momentum of light

TL;DR

This paper demonstrates that the orbital angular momentum of light can induce the inverse Faraday effect in metals, expanding the understanding beyond the traditional spin angular momentum origin and offering new control methods for optomagnetic phenomena.

Contribution

It provides the first evidence that orbital angular momentum of light can induce the inverse Faraday effect in metals, supported by a hydrodynamic model and numerical simulations.

Findings

OAM contributes to the inverse Faraday effect in gold films.

The relative contributions of SAM and OAM depend on beam focusing.

OAM offers a new degree of freedom for controlling optomagnetic fields.

Abstract

It is usually admitted that the inverse Faraday effect (IFE) originates from the spin angular momentum (SAM) of light. In this paper, we evidence that part of the IFE in a metal is induced by the orbital angular momentum (OAM) of light. On the basis of a hydrodynamic model of the conduction electron gas, we describe the dependence of the IFE on the spin and orbital angular momenta as well as spin-orbit interaction in a non-paraxial light beam. We also numerically quantify the relative contributions of the SAM and OAM of light to the IFE in a thin gold film illuminated by different focused beams carrying SAM and/or OAM. The OAM of light provides a new degree of freedom in the control of the IFE and resulting optomagnetic field, thus potentially impacting various research fields including all-optical magnetization switching and spin-wave excitation.