Optical properties of a noble metal with a string-of-pearls insulator inhomogeneity

The configuration obtained by extracting, from the half space occupied by a noble metal, the material contained in the layer between two (in the mean parallel) periodic surfaces (gratings) and replacing it by an insulating material, is termed a string-of-pearls medium (SOPM). It reduces to a parallel-plane layered bicomposite medium (PPLBCM) for vanishing grating amplitudes and to a perfect mirror (PM) in the absence of the insulating layer. The spectra of the reflectivity for p-polarized incident light relative to the PM and PPLBCM are featureless, whereas those for the SOPM contain a series of spikes indicative of resonant coupling to the hybrid surface plasmons which are identified herein to be those associated with the eigenmodes of the PPLBCM.