Light scattering from self-affine fractal silver surfaces with nanoscale cutoff: far-field and near-field calculations.
We study the light scattered from randomly rough, one-dimensional, self-affine fractal silver surfaces with nanoscale lower cutoff illuminated by s- or p-polarized Gaussian beams a few micrometers wide. By means of rigorous numerical calculations based on the Green's theorem integral equation formulation (GTIEF), we obtain both the far- and near-field scattered intensities. The influence of diminishing the size of the fractal lower-scale irregularities (from approximately 50 nm to a few nanometers) is analyzed in the case of both single realization and ensemble-average magnitudes. For s polarization, variations are small in the far field, being significant only in the higher-spatial-frequency components of evanescent character in the near field. In the case of p polarization, however, the nanoscale cutoff has remarkable effects stemming from the roughness-induced excitation of surface-plasmon polaritons. In the far field, the effect is noticed both in the speckle pattern variation and in the decrease of the total reflected energy upon ensemble averaging, as a result of increased absorption. In the near field, more efficient excitation of localized optical modes is achieved with smaller cutoff, which in turn leads to huge surface electric field enhancements.
Sánchez-Gil
José A
JA
Instituto de Estructura de la Materia, Consejo Superior de Investigaciones Científicas, Madrid, Spain. j.sanchez@iem.cfmac.csic.es
García-Ramos
José V
JV
Méndez
Eugenio R
ER