Here we experimentally demonstrate the topological Faraday effect—the polarization rotation caused by the orbital angular momentum of light. It is found that the Faraday effect of the optical vortex beam passing through a transparent magnetic dielectric film differs from the Faraday effect for a plane wave. The additional contribution to the Faraday rotation depends linearly on the topological charge and radial number of the beam. The effect is explained in terms of the optical spin-orbit interaction. These findings underline the importance of using the optical vortex beams for studies of magnetically ordered materials.

Here we theoretically and experimentally demonstrate a way to control the intensity of optical vortices by a magnetic field directed along the beam axis. We describe the principle of an optical vortex modulator and switch based on the Faraday effect in an iron garnet film. Importantly, the magnetic field influences only the polarization plane of the vortex and keeps its topological charge.

The phenomena of magneto-optical polarization rotation and circular magnetic dichroism are well known in the Faraday configuration. We present another effect, an odd magneto-optical linear dichroism, arising in nanostructures with polarization-dependent mode Q-factors and magneto-optical components. It reveals itself as the magneto-optical modulation of light intensity for the two opposite magnetization directions in the Faraday configuration. The effect was demonstrated on a magnetophotonic crystal with a cavity mode, the polarization-dependent Q-factor of which is due to oblique incidence. For a polarization angle of 60° (or 120°) and an angle of incidence around 60°, the magneto-optical intensity modulation maximizes and reaches 6%.