  This work presents numerical and experimental results of plasmonic
Metal-Insulator optical nano-cavities. The systems are composed of Silver as
metal, polyvinylpyrrolidone or indium tin oxide or zinc oxide as insulator. The
proposed nano-cavities exhibit extraordinary effects as colors changing in
function of the incident/view angles, enhancement of the experimental real and
imaginary parts of the pseudo dielectric constant, an extraordinary
transmission of 50$\%$ and zero reflection for both polarizations at the
resonant wavelengths. These results lead to the formation and propagation of
surface plasmon polaritons and their hybridization in gap surface plasmons. The
concurrence of these effects allow studying the Goos-H\"anchen shift by
exploiting the very narrow $\Delta$ and $\Psi$ ellipsometer parameters. Thank
to their optical properties, the proposed nano-cavities could be applied in
several fields such tunable color filters, optics, photonics and sensing.
