Analysis of the extreme scattering effect for particles inside and above a noble metal film via the discrete sources method

In this paper the discrete sources method is applied to analyze the extreme scattering effect for particles located both inside and on a gold film deposited on a glass prism. The extreme scattering effect is an effect of the sharp increase of the scattered intensity for P-polarized excitation which occurs in the evanescent wave region behind the critical angle. Moreover, the intensity enhancement appears not only in the transmission direction but in the backscattering direction as well. The effect does not depend on the thickness of the metal film or particle diameter, but it is strongly affected by the film material. Different scattering characteristics, such as transmission cross section and reflection cross sections and their correlation with the surface plasmon resonance in the film, are investigated and discussed in this paper. The analysis of the influence of a thin transparent spacer layer between particle and gold film on the scattering characteristics has been performed. The differential scattering cross section is considered to examine the field distribution in the forward and backscattering directions.