  Plasmonic metasurfaces are investigated that consist of a sub wavelength line
pattern in an ultrathin (~ 10 nm) silver film, designed for extraordinarily
suppressed transmission (EOST) in the visible spectral range. Measurements with
a near-field scanning optical microscope (NSOM) demonstrate that far field
irradiation creates resonant excitations of antenna like (bright) modes that
are localized on the metal ridges. In contrast, bound (dark) surface plasmon
polaritons (SPPs) launched from an NSOM tip propagate well across the
metasurface, preferentially perpendicular to the grating lines.
