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It has recently been found that the intensity of the electric
near field of a triangular aperture in a metal film is strongly localized
at one edge of the aperture for incident light polarized
perpendicular to this edge. Previous numerical calculations of
the near field of a triangular aperture in a planar metal film,
using the field susceptibility technique, yielded a nearly quantitative
agreement with the experiments. Using this numerical
technique, the influence of an obliquely
incident plane wave on the near field of small circular and triangular
apertures has been investigated. An interpretation of the numerical results
leads to a deeper understanding of the way in which light transmission
through the aperture is excited. The data suggest that
after excitation of currents in the metal film by the incident
light, a scattering of these currents by the aperture generates the
near field of the aperture. Researchers found that the excitation of small
apertures (size < 100 nm) is due to a tangential magnetic field
whereas the perpendicular electric field plays no role. The excitation
of a small aperture can thus be described exclusively
by a magnetic polarizability. It has been pointed out that for thin metal films
an interference of the scattered field with the field transmitted
through the metal film changes the near field pattern.
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