Abstract:
The homogeneous optical response in conducting nanostructured layers, and in insulating layers containing dense arrays
of self assembled conducting nanoparticles separated by organic linkers, is examined experimentally through their
effective complex indices (n*, k*). Classical effective medium models, modified to account for the 3-phase
nanostructure, are shown to explain (n*, k*) in dense particulate systems but not inhomogeneous layers with
macroscopic conductance for which a different approach to homogenisation is discussed. (n*, k*) data on thin granular
metal films, thin mesoporous gold, and on thin metal layers containing ordered arrays of voids, is linked to properties of
the surface plasmon states which span the nanostructured film. Coupling between evanescent waves at either surface
counterbalanced by electron scattering losses must be considered. Virtual bound states for resonant photons result, with
the associated transit delay leading to a large rise in n* in many nanostructures. Overcoating n-Ag with alumina is
shown to alter (n*, k*) through its impact on the SP coupling. In contrast to classical optical homogenisation, effective
indices depend on film thickness. Supporting high resolution SEM images are presented.
