Extraordinary transmission through a single coaxial aperture in a thin metal film

TL;DR

This study demonstrates that a single sub-wavelength coaxial aperture in a thin metal film can significantly enhance light transmission when illuminated with radially polarized light, with potential applications in nanophotonics.

Contribution

We experimentally show enhanced transmission through a single coaxial aperture using radially polarized light, supported by FDTD simulations, revealing polarization effects and plasmonic influences.

Findings

Up to four times transmission enhancement compared to circular apertures

Strong polarization contrast between radial and azimuthal illumination

Transmission can be suppressed by surface plasmon excitation

Abstract

We investigate experimentally the transmission properties of single sub-wavelength coaxial apertures in thin metal films (t = 110 nm). Enhanced transmission through a single sub-wavelength coaxial aperture illuminated with a strongly focused radially polarized light beam is reported. In our experiments we achieved up to four times enhanced transmission through a single coaxial aperture as compared to a (hollow) circular aperture with the same outer diameter.We attribute this enhancement of transmission to the excitation of a TEM-mode for illumination with radially polarized light inside the single coaxial aperture. A strong polarization contrast is observed between the transmission for radially and azimuthally polarized illumination. Furthermore, the observed transmission through a single coaxial aperture can be strongly reduced if surface plasmons are excited. The experimental results are in good agreement with finite difference time domain (FDTD) simulations.