Local circular polarization observed in surface vortices of optical near-fields

We demonstrate local circular polarization in surface vortices of an optical near-field generated by superposing two cross-propagating evanescent waves with transverse electric fields on a planar dielectric surface. The circularly rotating local electric fields are converted into circularly polarized propagating light waves in free space via a near-field interaction with a sub-wavelength size local probe. The results show that optical near-fields generated under the influence of a material environment with local rotational symmetry carry angular pseudo-momentum with respect to the symmetry axis. The local circular polarization is of fundamental significance in spin-related and magneto-optical phenomena in nanophotonics.