Theory on the scattering of light and surface plasmon polaritons by   arrays of holes and dimples in a metal film
  The scattering of light and surface plasmon polaritons (SPPs) by finite arrays of either holes or dimples in a metal film is treated theoretically. A modal expansion formalism, capable of handling real metals with up to thousands of indentations, is presented. Computations based on this method demonstrate that a single hole scatters a significant fraction of incoming light into SPPs. It is also observed that holes and dimples scatter SPPs into light with similar efficiencies, provided the depth of the dimple is larger than its radius. Finally, it is shown that in arrays the normalized-to-area emittances in the out-of-plane and SPP channels present different dependences with the number of holes. 
F. de Leon-Perez, G. Brucoli, F. J. Garcia-Vidal, and L. Martin-Moreno