  We theoretically investigate the generation of far-field propagating optical
beams with a desired orbital angular momentum by using an archetypical
magnetoplasmonic tip surrounded by a gold spiral slit. The use of a magnetic
material can lead to important implications once magneto-optical activity is
activated through the application of an external magnetic field. The physical
model and the numerical study presented here introduce the concept of
magnetically tunable plasmonic vortex lens, namely a magnetoplasmonic vortex
lens, which ensures a tunable selectivity in the polarization state of the
generated nanostructured beam. The presented system provides a promising
platform for a localized excitation of plasmonic vortices followed by their
beaming in the far-field with an active modulation of both light's
transmittance and helicity.
