Realization of an evanescent Bessel beam via surface plasmon interference excited by a radially polarized beam.

We report the experimental confirmation of the evanescent Bessel beam generation via surface plamson resonance excitation with a radially polarized beam. The interference of surface plasmon waves excited by a radially polarized beam creates an evanescent Bessel beam with enhanced localized field and spot size beyond the diffraction limit. The excitation of the surface plasmon is confirmed by the observation of a narrow dark ring at the back focal plane. Two-dimensional intensity distributions at different distances from the sample surface are mapped by a collection-mode near-field scanning optical microscope to verify the nondiffracting and decaying natures of the evanescent Bessel beam.