Direct Observation of Strong Localization of Quasi-Two-Dimensional Light
Waves
Mikroelektronik Centret
Technical University of Denmark
Scattering of surface plasmon polaritons on rough metal surfaces
is investigated by using scanning near-field optical microscopy. Different
scattering regimes, i.e., single, double, and multiple scattering, are
observed and related to the spatial Fourier spectraof near-field optical
images. For the regime of strong multiple scattering, the near-field optical
images exhibit spatially localized (within 150-250 nm) intensity enhancement
by 10-50 times. This feature is attributed to strong localization of surface
polaritons due to interference effects in multiple scattering caused by
surface roughness. Similar bright light spots are observed with light scattering
by silver colloid clusters on glass substrates. Differencies and similarities
in these scattering phenomena are discussed.