Electromagnetics of Complex Media and Boundary Conditions, Metamaterials, and Metasurfaces

Abstract

The research that is reported in this thesis focuses on the subject of tuning the properties of metamaterials. Once particles and objects composed of metamaterials are exposed to electromagnetic waves, their shape, size, and other geometric parameters play a vital role in their global response. The predominant goal of this study is to identify some of their salient features such as scattering, reflection and transmission, angular and spatial Goos Hanchen shifts (GHS) ¨ that could be used to analytically describe the behavior of metama terials and metasurfaces. The discussion has been started by analyzing the electromagnetic response of an active scatterer. With the time-harmonic convention exp(iωt) for temporal field variation, a material is dielectrically ac tive, if it has a negative imaginary part of the relative permittiv ity. Using the Lorenz-Mie theory and numerical surface-integral equation computations, calculations have been done regarding the scattering, absorption, and extinction cross sections of spherical scat terers with arbitrary material characteristics and diameters. Among other interesting characteristics, one prominent aspect of electro magnetically active particles is their strong back-to-front scattering ratio, as they tend to direct scattering into the backward half-plane. Moreover, by analyzing the extinction characteristics of active scat ters, an innovative classification of the objects has been mentioned, depending on the sign (positive, zero, or negative) of the extinction cross-section. Furthermore, using the Lorentz-Drude model, analysis has been made to investigate the reflection/transmission characteristics and GHS for uniaxial left-handed metamaterials in the presence of losses. Convergence of the results, with the observations already reported in the literature, has also been examined while taking the lossless situation into consideration. It has been noted that by introducing an appropriate amount of losses, one can control the behavior of the GHS very effectively to meet the design requirements. The study has been further extended by examining the characteristics of the plane wave incident at the isotropic fractal dielectric-anisotropic chiral interface. Reflection, transmission, and GHS have been ana lyzed with respect to the incident angle, permittivity, chirality, and dimension of the medium. The impact of medium parameters has also been carefully examined for the purpose of tuning the GHS. Moreover, theoretical analysis of the angular and spatial GHS of Gaussian beams incident on cross anisotropic metasurface coated interface from active medium to air has been conducted. By consid ering the TE and TM polarizations of the incident Gaussian beam, it is highlighted that, for the TE-polarized beam, a huge amount of negative and positive shifts are induced by changing the permittiv ity of the active medium. Thus, this analysis adds to the refinement of the angular and spatial GHS using an active (gainy) medium and may offer the potential to contribute to various useful applications of metamaterials and metasurfaces