Plasmon Resonances in a Convex-Concave Silver Nanocylinder

The paper considers a two-dimensional problem of diffraction of a plane electromagnetic TM-type wave on a cylindrical silver nanostructure the cross-sectional contour of which is a convex-concave curve (Cassini oval). In the light wavelength range 300 nm < lambda < 900 nm the spectra of the scattering diameter and the scattering diagrams were calculated by a rigorous numerical method. The influence of the losses of the medium, the geometric dimensions of the structure, and the angle of incidence of a plane wave on the scattering diameter and the scattering diagram are investigated. It is shown that in quasi-static region kD < 1 (k = 2 pi/lambda, D is the maximum size of the structure, lambda is the wavelength) the presence of the concavity of the scatterer contour leads to the formation of additional (in comparison with the case of a convex contour) maxima of the scattering diameter. A decrease in the value of the minimum of the scattering diameter by three to four orders of magnitude was found.