Electromagnetic theory of helicoidal dichroism in reflection from magnetic structures
Mauro Fanciulli, David Bresteau, Mekha Vimal, Martin Luttmann, M. Sacchi, Thierry Ruchon
Abstract
We present the classical electromagnetic theory framework of reflection of a light beam carrying orbital angular momentum (OAM) by a magnetic structure with generic symmetry. Depending on the magnetization symmetry, we find a change in the OAM content of the reflected beam due to magneto-optic interaction and an asymmetric far-field intensity profile. This leads to three types of magnetic helicoidal dichroism (MHD), observed when switching the OAM of the incoming beam, the magnetization sign, or both. In cases of sufficient symmetries, such as domain walls and magnetic vortices, we establish analytical formulas that link an experimentally accessible MHD signal to the magneto-optical Kerr effect (MOKE) constants.