Statistics of local field intensity enhancements at nanostructured surfaces investigated with a near-field optical microscope - art. no. 115414

Near-field intensity distributions measured at nanostructured surfaces with a scanning near-field optical microscope are treated to determine the stat istics of local field intensity enhancements. The probability density funct ion (PDF) of the field intensity enhancement is calculated for surface-plas mon-polariton scattering by randomly rough surfaces of thin metal films and for light scattering in silver colloid fractals. We demonstrate that the s tatistics of the intensity distributions established in different scatterin g regimes, viz., single and multiple scattering, is distinctly different, a nd compare our results with the theoretical predictions available. We show that. in the regime of multiple scattering, the PDF decreases exponentially for large values of the intensity enhancement with the slope for surface-p lasmon scattering being significantly different from that for light scatter ing in surface fractal structures. We also find that, in the latter case, t he PDF slope is only weakly influenced by variations in the wavelength and polarization of incident radiation.