DEGENERATE LONG-RANGE SURFACE-MODES, SUPPORTED ON THIN NICKEL FILMS

In this work islandised nickel films have been placed in a symmetric e nvironment to allow optical excitation of long-range surface modes via attenuated total reflection. Comparison of modelling theory to the ex perimental angle-dependent reflectivity data shows that it is not poss ible to determine the optical permittivity of the thin nickel layer wi thout knowledge of its thickness, The reflectivity data has a set of d egenerate fits: the deduced optical permittivities for this degeneracy describing a circle when plotted as a Cole-Cole plot. This circle is naively predicted from an analytical three-media theory which ignores the coupling prism. Moreover, further investigations show that the deg enerate circle is a general result of fitting reflectivity curves in t he vicinity of a long range mode.