Plasmon Resonances in Square and Rectangular Noble Metal Nanoplates

Abstract

Abstract—The article considers the two-dimensional diffraction problem of a TM-type plane electromagnetic wave on a cylindrical silver or gold structure, the contour of the cross section of which is a square or rectangle. In the wavelength range $$300\,\,{\text{nm}} < \lambda < 900\,\,{\text{nm}}$$ a rigorous numerical method is used calculate the spectra of the scattering cross section and scattering patterns. The influence of losses of the medium, the geometric dimensions of the structure, and the angle of incidence of a plane wave on the scattering cross section and scattering pattern is studied. It has been shown that the real losses of gold make it impossible for multipole resonances to exist at plate sizes substantially less than the wavelength. In the case of a silver plate, the position of the dipole and the presence of multipole resonances depends both on the length and thickness of the plate and on the angle of incidence of the plane wave.