Shining light through an aperture that is smaller than the wavelength of the light generally is a rather inefficient process. However, recent experiments with metal sheets decorated with a periodic array of submicrometer perforations have displayed enhanced light transmittance in certain spectral regions. Analysis of those early results suggested that the light got a helping hand through the holes by tunneling through surface plasmons, which are electronic excitations induced by and coupled with the interaction between the incident light and the electrons near the metallic surface.
Two studies now verify that initial hunch and reveal further insights into the physical processes involved. The calculations of Martín-Moreno et al. show that light is transmitted via surface plasmon molecules (pairs of coupled plasmons on either side of the metal sheet) through thin films and that this mechanism evolves into tunneling between two isolated plasmons as the thickness of the sheet is increased. Approaching the problem from a different direction, Salomon et al. show that electromagnetic coupling between the perforations results in the same enhancement of transmission. -- ISO
Phys. Rev. Lett. 86, 1114 (2001); Phys. Rev. Lett. 86, 1110 (2001).
