Image dipole effects are highly dependent on the polarization direction, constructive (destructive) for the vertical
(horizontal) dipole with respect to the interface, respectively. Polarization resolved detection of light scattered off a gold
nano particle functionalized tip on a flat gold surface enables the study of the image dipole orientation effects on the
scattering type near field scanning optical microscope signal. A propagating surface plasmon polariton as an excitation
source sufficiently reduced the large background by virtue of its evanescent nature capacitating the quantitative
description of the image dipole. At large tip-to-sample distances, the Fabry-Perot like interference between the radiations
from the GNP and from the image dipole induced at the flat gold surface, are evident. The horizontal- polarization and
vertical-polarization Fabry-Perot oscillations, however, are out-of-phase with each other. As the tip approaches the
surface, the vertical component get further enhanced while the horizontal one gets suppresses, demonstrating the
polarization reversal of image dipole as predicted by theory.
We study the dielectric constant dependent diffraction phenomena of single slit apertures, both theoretically and
experimentally. We experimentally simulate perfect metal and real metal cases by investigating subwavelength
diffraction by a single slit, both in nano-optical and in terahertz regimes, keeping the slit-width/wavelength ratio
approximately the same for both of frequency regimes. The wave-front in optical regime separates itself into forward
propagating beam and surface-bound 90-degree diffracted wave, i.e., surface plasmon polaritons; while the separation of
modes is not observed in terahertz regime.