Investigation of electric field enhancement between metal blocks at the focused field generated by a radially polarized beam

Abstract

A radially polarized beam possesses peculiar focusing properties compared with a linearly polarized beam, for example, the generation of a strong longitudinal field and zero intensity of the Poynting vector on the beam axis. In order to exploit these focusing properties, here we consider a system in which gold metal cubes are arranged along the propagation direction of the beam. An electric field enhancement of more than 20-times can be generated between two gold cubes separated by a distance λ/10 on the optical axis. This is because the energy of a radially polarized beam can propagate even if a metal cube is located on the beam axis, and a longitudinal field generated between the cubes can induce a surface plasmon mode. We show that these results are peculiar properties that cannot be produced with an incident linearly polarized beam. We also show that the beam can generate multiple regions of electrical field enhancement in the propagating direction when multiple metal cubes are arranged on the beam axis.