  The tailoring of plasmonic near-fields is central to the field of
nanophotonics. The detailed knowledge of the field distribution is crucial for
a design and fabrication of plasmonic sensors, detectors, photovoltaics,
plasmon-based cicuits, nanomanipulators, electrooptic plasmonic modulators and
atomic devices. We report on a fully quantitative comparison between near field
observation and numerical calculations, considering the intensity distribution
for TM and TE polarisations, necessary for the construction of devices in all
these areas. We present the near field scanning microscopy (NSOM) results of
Surface Plasmon Polaritons (SPPs), excited by linearly polarized illumination
on a gold, nanofabricated transmission grating. The optimization process is
performed for infrared light, for future applications in cold atoms trapping
and plasmonic sensing. We show the in situ processes of build up and
propagation of SPPs and confirm that the out of plane component is not coupled
to the aperture-type NSOM probe.
