Evidence for radiative damping in surface-plasmon-mediated light transmission through perforated conducting films

Surface plasmon polaritons are believed to be responsible for higher-than-expected light transmission through metallic films with subwavelength aperture arrays. Here we report the effect of aperture size increase on far-infrared transmission characteristics of such perforated films. The observed increase in the transmission efficiency and the redshift of the resonance frequency are consistent with a published theoretical model, which identifies radiation damping of surface plasmon polaritons as the driving mechanism behind these spectral changes. Optical properties of films with different lattice and aperture configurations, however, are found to respond distinctly to aperture enlargement and indicate the critical role of these parameters on the scattering of surface plasmon polaritons into electromagnetic radiation. The effects of radiation damping are also recognized in the angular dependence of the transmission spectra. (C) 2003 Optical Society of America.