SCATTERING OF LIGHT FROM A THIN METALLIC FILM WITH A SHALLOW RANDOM ROUGH SURFACE BETWEEN DISSIMILAR MEDIA .1. THEORY

摘要

The reflected field scattered from a thin metallic film with a shallow rough random surface bounded by two semi-infinite dissimilar optical media is calculated. The model assumes that all media are homogeneous, isotropic, non-magnetic, linear and may be characterized by a frequency dependent complex dielectric function. The Rayleigh hypothesis is used to obtain an independent integral equation relating the amplitudes of the reflected fields to the incident wave. This treatment is valid for both TM(p) or TE(s) polarizations. Numerical results are obtained by assuming a Gaussian roughness spectrum for the random rough surface and the formalism is applied to simulate the scattering in the ATR-Kretschmann configuration, allowing the excitation of surface plasmons (SP), prism-metal-air. The angular dependence of the incoherent scattering shows two enhancement peaks, in addition to the well known backscattering effect. The angular positions of these two peaks are about the angle of excitation of SP (+/- theta(sp)) and are independent of the angle of incidence theta(i). They appear only for p-polarized light and are due to single-scattering effects. When theta(i) is tuned at exactly -theta(sp) the enhanced backscattering peak is screened by the peak located at this angle and the background incoherent scattering is two orders of magnitude higher for the same response computed for all other angles of incidence theta(i). (C) 1997 Elsevier Science B.V. [References: 20]