The Electromagnetic Characteristics Of Electromagnetic Metamaterials And Its Applications Based On Optical Transformations

Electromagnetic metamaterial, a new and interdisciplinary field, has been received more and more attentions in the past ten years, for its potential development prospects. In this thesis, based on the electromagnetic response characteristics of the metamaterials, we construct new types single-sided structure left-handed metamaterials, and design a high dimensional four-fold C-shaped planar left-handed metamaterial, which can be reduce the effect of EM wave propagation direction on the metamaterial's response; then we discuss the electromagnetic coupling between the single-ring SRRs (split-ring resonators) with different gaps (1-gap,2-gaps, and 4-gaps), and the splitting of the magnetic resonance caused by the electromagnetic coupling. Furthermore, based on the optical transformations, we discuss the applications of electromagnetic metamaterials in the controlling of electromagnetic wave, such as wave bender and invisible cloak.In the first part of this thesis, we investigate numerically the constructions of new types electromagnetic metamaterials, and their's electromagnetic responses to the incident EM wave. Firstly, we detail analyze the negative refraction properties of different left-handed metamaterials (LHMs), of which the Rods (or cut wire) are printed in-plane, off-plane, and connected with respect to the symmetric paried split-ring resonator, respectively. With the simulation results, we conclude that the conncected case single-sided LHM can exhibit a simultaneous low-loss and broad left-handed pass-band, compared with the in-plane and off-plane cases.Secondly, we design a single-sided, easy fabricated left-handed metamaterial with double L-shaped resonator inclusions. In order to verify our design, both the numerical and experimental demonstrations are carried out, and the results agree well to each other. Then, the mechanism of negative refraction and the cause of two magnetic resonances of the double L-shaped resonator are detail explained and analyzed.Thirdly, we design and investigate a high dimensional four-fold C-shaped planar left-handed metamaterial, it can exhibits negative refraction with electromagnetic wave incidence in three different directions and with different polarizations. So it can reduces the effect of electromagnetic wave paopagation direction on the metamaterial's response. Furthermore, the mechanism of the negative refraction and the electromagnetic responses of the four-fold C-shaped planar metamaterial to EM wave are discussed under the normal and parallel incidence case, respectively; and the left-handed property of this metamaterial is also demonstrated numerically.Lastly, we investigate the electromagnetic response of the single ring resonator with 1-gap,2-gaps, and 4-gaps, respectively. From the simulation results, we conclude that the electromagnetic coupling between the rings becoming stronger with the gaps increase; and the magnetic resonace mode will be splitted into two modes, due to the strong coupling between the neighbor rings for the 4-gaps case. Also, we construct a negative meganetic metamaterial with super-wide band-gap by asjusting the geometric parameters of the 4-gaps split-ring resonator.In the second part of this thesis, based on the optical transformations, we discuss numerically the application of electromagnetic metamaterials in controlling the EM wave. Firstly, we design a multi-branch wave bender by using finite embedded optical transformations, which can bents the electromagnetic wave simultaneously to different directions with different angles without reflection. Furthermore, we extend this wave bener, and design a crossed two branches wave bender, it can also bent the electromagnetic wave to the desired directions without reflection, though there exists coupling between two branches, and the wave shape is a little destroyed. Secondly, we investigate the impedance-matched problem between the boundaries of the combined cloaks, and the scattering of the electromagnetic cloak is substantially reduced after we have reasonably designed and modified the electromagnetic constitutive parameters of the cloak. Then, the full wave simulations are also carried out to demonstrate our designs and calculations.