Nanostructure porous films with arrays of gold nanoparticles (Au NPs) have been produced
by pulsed laser deposition. Dispersion properties of surface plasmons have been studied by
the modulation-polarization spectroscopy technique. The dispersion relations for radiative
modes and two types of non-radiative modes of localized and propagating surface plasmons
were obtained. The branches of propagating modes were characterized by negative group
velocity caused by spatial dispersion of dielectric function. The propagating modes are …