We present a study on the far-field patterns of light transmitted through sub-wavelength metallic hole-arrays. Spectral imaging measurements are used here on hole arrays for the first time. It provides both spatial and spectral information of the transmission in far-field. The visibility of the images, measured in two illumination modes: Köhler and collimated, is calculated for different planes in and out of focus. The transmission under collimated illumination reveals that 75% of the beam if non-divergent. The results are in agreement with the low divergence measured by Lezec [Science 297, 820 (2002)].

We present an experimental analysis of the plasmonic scattering properties of gold nanoparticles controllably placed nanometers away from a gold metal film. We show that the spectral response of this system results from the interplay between the localized plasmon resonance of the nanoparticle and the surface plasmon polaritons of the gold film, as previously predicted by theoretical studies. In addition, we report that the metal film induces a polarization to the single nanoparticle light scattering, resulting in a doughnut-shaped point spread function when imaged in the far-field. Both the spectral response and the polarization effects are highly sensitive to the nanoparticle–film separation distance. Such a system shows promise in potential biometrology and diagnostic devices.

We present a theoretical foundation for the beaming of light displayed by a single subwavelength aperture in an appropriately corrugated metal film [H. J. Lezec, Science 297, 820 (2002)]]. Good agreement is found between calculations and experimental data. We show that beaming is due to the formation of electromagnetic surface resonances and that the beam direction, width, and wavelength at which it occurs can be selected by tuning geometrical parameters of the structure.