OPTICAL-PROPERTIES OF HIGHLY ROUGH SURFACES AND ISLAND FILMS

This study treats the optical properties of different two-dimensional inhomogeneous systems in which localized and delocalized surface modes excited by incident light can exist. The optical response is described with the use of kinetic equations linking together different types of surface modes. It is important that both electromagnetic interactions between local modes and the dependence of the optical characteristics of centers on the local geometrical structure are taken into account. Exact solutions have been obtained of the homogeneous problem and of the problem for quasi-one-dimensional distribution of local centers. It is shown that the behavior of experimentally observable quantities (enhancement ratio of the field at the surface, effective dielectric constant of the surface layer, etc.) as functions of the frequency and concentration of local centers depends essentially on the excitation mechanism of local modes. A problem for centers located on the Cayley tree with coordination number equal to three is given an approximate consideration. It is shown that the imaginary part of the effective dielectric constant has a casp singularity (derivative discontinuity) at the percolation threshold. © 1990.