Metamaterials: Characterization, Bianisotropy, And Applications

The emergence of artificially designed subwavelength electromagnetic materials, de-noted "metamaterials", have significantly broadened the range of material responses found in nature. Since its first experimental demonstration less than 10 years ago, metamaterial has developed as a rapidly growing multidisciplinary branch of science and engineering.By engineering the internal structure of metamaterials it is possible to create effective electro-magnetic properties, including some which were previously unavailable.This dissertation presents the design of a novel bianisotropic metamaterial firstly, and then explores the per-tinent applications by taking advantage of all the fascinating and versatile electromagnetic properties.The contents can be summarized as follows:1.The refraction and propagation properties of metamaterials with bianisotropic effects are investigated, the dispersion relation can be strongly influenced by the inclusion of chirality. A realization of the bianisotropic metamaterial based on S-ring resonators is proposed, by subtly shorting some horizontal metallic strips inside it. The structure is theoretically analyzed from a microscopic viewpoint, and the constitutive param-eters are characterized, where a nonzero chirality component is clearly shown.Both the numerical simulation and experiment measurement show strong cross polariza-tion effects when waves are incident onto a slab of this material, further confirming the prediction by our theoretical analysis.2.The chiral nihility effects are illustrated by showing the propagation of a Gaussian beam, both reflected and refracted from an air-chiral interface, and through layered chiral nihility media that are matched to free space.The critical angle for total reflec-tion and the index-matched total transmission in a matched chiral half-space, along with the wave splitting, wave widening, and a wave of "standing phase" in matched chiral nihility slabs, are demonstrated. 3.The backscattering properties of a PEC sphere coated with layered anisotropic me-dia, whose constitutive parameters are close to nihility, are studied.Compared with isotropic case, the anisotropic media with small axial parameters have the poten-tial to yield more reduction of backscattering magnitude, which can be used as an invisibility cloak in monostatic radar system.4.According to cloak parameters from optimization, which are totally different from those given by coordinate transformation approach, a well-designed cloak for a PEC cylinder is simulated to perform almost the same invisibility effect, but with much simpler parameters and may be easier to fabricate.5.The case where the background material of a cloak possesses magnetoelectric cou-pling is discussed, including bianisotropic media or isotropic moving with uniform speed which may be comparable with that of light. The specifically proposed consti-tutive parameters for such cloak own more complicated bianisotropy, which can not be simply produced by an isotropic medium in a uniform-velocity motion.6. The imaging method when an obstacle presents in between the target and the sensor is demonstrated, using the concept of active metamaterial.The obstacle's impact to the reflection coefficients can be canceled by imaginatively adding an opposite layer, leading to a significant improvement of the target imaging. When the obstacle layer is inhomogeneous due to its small defects, a homogenization procedure based on the Drude model is applied to characterize its effective constitutive parameters. The effectiveness of the proposed method has been proved through our calculation examples.