The interaction of light with metallic microparticles and nanoparticles is strongly modified by resonance effects such as plasmon-polaritons. Size, shape and material of the structures affect the spectral angular scattering distribution. To date only model calculations of light scattering by simple shapes are available. To test analytical and finite element models both near field and far field measurements have been carried out[1,2].

The nanoparticles and microparticles were created with colloidal crystals. Metal evaporation created arrays of triangular particles. Other structures were created by transforming the adsorbed colloidal spheres, by embedding them or by transforming the arrays of metal particles.

The samples were illuminated either in total internal reflection geometry or with light perpendicularly incident on the plane of the particles. Near field measurements were carried out in a WITec alphaSNOM. Scattering data was acquired both with a confocal microscope and with a goniometer setup.

SNOM measurements and confocal microscopy data are compared to model calculations. It was observed that the shape of the particles and their material composition have a strong influence of the intensity distribution in Bragg diffraction patterns.

1. A. Siegel, M. R. Gonçalves, R. Ameling, and O. Marti, "Investigation of the light scattering form factor of metallic nanostructures using Bragg diffraction", Journal of Optics A accepted for publication (2007).
2. M. R. Gonçalves, A. Siegel, and O. Marti, "Influence of the light scattering form factor on the Bragg diffraction patterns of arrays of metallic nanoparticles", Journal of Microscopy accepted for publication (2007).

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