Sharif Digital Repository

Due to the growing need for plasmonic wavs in microwave and terahertz spectra, a periodic arrangement of one-dimensional cut-through slits is investigated and an equivalent model based on the effective medium theory is derived. In contrast to the all previous attempts that were successful in mimicking only the zeroth-order diffracted waves, the proposed effective medium is capable of mimicking all diffraction orders. The parameters of the equivalent model are established by comparing the scattered waves of the semi-homogeneous medium and those of the main structure obtained by invoking the rigorous mode matching approach based on the single mode approximation inside the slits. This medium is... 

Excitation of Localized Surface Plasmons, which is one of the features of the metal nanostructures, results in the confinement of light in the dimensions smaller than the incidence wavelength, and even lower than the fundamental diffraction limit. This property causes electric field enhancement at surface, helping the occurrence of Surface Enhanced Raman Scattering (SERS). The amount of electric field enhancement and its resonance frequency depend on the type of material, its geometrical properties and its shape, and the arrangement of the scattering particles. Also, properties of surrounding environment material and the type of the excited mode of the structure, and the incidence wave... 

In this thesis we investigate the use of periodic array of metallic structures which mimics the propagation of the surface plasmon-polaritons waves. The TEM modes supported by these structured surfaces are referred to as the spoof surface plasmon-polaritons. They have many properties in common with the electron plasma and can be described by a plasma-like effective permittivity, when the structure is on a scale much smaller than the wavelength. In this thesis we extend this concept to include different kinds of structured surfaces like cut through metallic slits array and square array of rectangular metallic pillars which support TEM modes. We show that although these structured surfaces...