Plasmon scattering from single sub-wavelength holes
  We map the complex electric fields associated with the scattering of surface plasmon polaritons by single sub-wavelength holes of different sizes in thick gold films. We identify and quantify the different modes associated with this event, including a radial surface wave with an angularly isotropic amplitude. This wave is shown to arise from the out-of-plane electric dipole induced in the hole, and we quantify the corresponding polarizability, which is in excellent agreement with electromagnetic theory. Time-resolved measurements reveal a time-delay of 38? +/- 18 fs between the surface plasmon polariton and the radial wave, which we attribute to the interaction with a broad hole resonance. 
N. Rotenberg, M. Spasenovic, T. L. Krijger, B. le Feber, F. J.   Garc{\i}a de Abajo, and L. Kuipers
cond-mat.mes-hall physics.optics