  Optical beams carrying orbital angular momentum (OAM) can find tremendous
applications in several fields. In order to apply these particular beams in
photonic integrated devices innovative optical elements have been proposed.
Here we are interested in the generation of OAM-carrying beams at the nanoscale
level. We design and experimentally demonstrate a plasmonic optical vortex
emitter, based on a metal-insulator-metal holey plasmonic vortex lens. Our
plasmonic element is shown to convert impinging circularly polarized light to
an orbital angular momentum state capable of propagating to the far-field.
Moreover, the emerging OAM can be externally adjusted by switching the
handedness of the incident light polarization. The device has a radius of few
micrometers and the OAM beam is generated from subwavelength aperture. The
fabrication of integrated arrays of PVLs and the possible simultaneous emission
of multiple optical vortices provide an easy way to the large-scale integration
of optical vortex emitters for wide-ranging applications.
