Transmission and reflection properties of layered left-handed materials
Author(s)Chen, Jianbing James, 1971-
Massachusetts Institute of Technology. Dept. of Electrical Engineering and Computer Science.
Jin Au Kong.
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This thesis is concerned with the reflection and transmission properties of layered left-handed materials (LHM). In particular, the reflection properties of (LHM) slabs are studied for the Goos-Hanchen (GH) lateral shift phenomenon. We demonstrate a unique GH lateral shift phenomenon, which shows that both positive and negative shifts can be achieved using the same LHM slab configuration. This phenomenon is different from previously established cases where the GH lateral shift can be only negative or only positive when different LHM slab configurations are used. We also show that there exist two distinct cases with this unique phenomenon. One case has two regions of incident angles where the GH lateral shift directions are different, while another case has three regions with alternated GH shift directions. A generalized analytical formulation for analyzing the GH lateral shift direction is provided, which reveals that this unique phenomenon is related to the relative amplitudes of the growing and decaying evanescent waves inside the LHM slabs. The energy flux patterns within LHM slabs are further studied to show the influence of the evanescent waves on the GH shift direction change.(cont.) Furthermore, the transmission property of LHM slabs are studied on the finite slabs' maging capability. First, the development of the numerical simulation tool - the Finite-Difference Time-Domain method (FDTD) - investigates the ability of the method to model a perfect lens made of a slab of homogeneous LHM. It is shown that because of the frequency dispersive nature of the medium and the time discretization, an inherent mismatch in the constitutive parameters exists between the slab and its surrounding medium. This mismatch in the real part of the permittivity and permeability is found to have the same order of magnitude as the losses typically used in numerical simulations. Hence, when the LHM slab is lossless, this mismatch is shown to be the main factor contributing to the image resolution loss of the slab. In addition, finite-size LHM slabs are studied both analytically and numerically since they have practical importance in the actual experiments. The analytical method is based on Huygens' principles using truncated current sheets that cover only the apertures of the slabs. It is shown that the main effects on the images' spectra due to the size of the slabs can be predicted by the proposed analytical method, which can, therefore, be used as a fast alternative to numerical simulations.(cont.) Furthermore, the property of negative energy streams at the image plane is also investigated. This unique property is found to be due to the interactions between propagating and evanescent waves and can only occur with LHM slabs, of both finite-size and infinite size. The last part of the thesis deals with multi-layered media for the application to antenna isolations. The setup is with two horn antennas located beneath the ground plane with 10 A distance apart. In order to reduce the coupling between antennas, multi-layered media placed on top of the ground plane need to be designed to suppress the fields. After the problem is simplified to the dipole antenna coupling in infinite slabs, the method to evaluate the fields inside layered media is presented. This method obtains the spectral domain Green's function first and then transforms the fields to the spatial domain using the Sommerfeld-type integration. After the method is validated using right-handed materials (RHM) from references, it is extended to include media like LHM as well as p. negative material and : negative material . The validation with these materials are done by comparing the results with CST microwave studio simulations. The first configuration for the antenna isolation design if one layer slab backed by the grounded plane. Two different approaches are used to find the optimum slab parameters for the isolation.(cont.) One approach is to use Genetic Algorithm (GA) to optimize the slab's constitutive parameters and the thickness for a minimum coupling level. The other approach is to develop an analytic asymptotic expression for the field, and then used the expression to design the slab parameters for the best isolation. We conclude that both approaches yield the same design for the given configuration. The effectiveness of the design is also validated on a grounded finite slab, which is the representation of the actual application. Finally, multi-layered media for the antenna isolation is studied. GA method is applied with an optimization scheme tailed for a five layered structure. We show that GA converges very fast to the solution and the result yields satisfactory isolation between the antennas.
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, February 2007.Includes bibliographical references (p. 179-189).
DepartmentMassachusetts Institute of Technology. Dept. of Electrical Engineering and Computer Science.; Massachusetts Institute of Technology. Department of Electrical Engineering and Computer Science
Massachusetts Institute of Technology
Electrical Engineering and Computer Science.