Magnetic helicoidal dichroism in reflection by magnetic vortices

TL;DR

This paper introduces Magnetic Helicoidal Dichroism (MHD), a novel optical technique using orbital angular momentum of light to identify and analyze complex magnetic vortex structures rapidly and with high precision.

Contribution

It presents a new method based on OAM coupling that enables quick, polarization-independent imaging of magnetic spin textures with ultrafast temporal resolution.

Findings

Enrichment of neighboring OAM modes upon reflection from magnetic vortices

Anisotropic far-field images reveal MHD signals

Precise retrieval of magneto-optical constants

Abstract

Identifying and imaging spin textures of ever more complex magnetic structures has become a major challenge in the past decade, especially at ultrashort timescales. Most of current approaches are based on the analysis of their polarization and magnetization-dependent reflectivities. Based on our joint publication XXX XX XXXXXX, we introduce a different concept, centered on the coupling of magnetic structures with light beams carrying orbital angular momentum (OAM). Upon reflection by a magnetic vortex, an incoming beam with a unique value $\ell$ of OAM gets enriched in the neighboring OAM modes $\ell\pm 1$. It results in anisotropic far-field images, which are identified as a Magnetic Helicoidal Dichroism (MHD) signal. Their analysis allow to retrieve the complex magneto-optical constants with excellent precision. This method, which does not require any polarization-resolved analysis, is promising for a quick identification of spin textures, including with attosecond to femtosecond time resolutions.