Theory and application of left-handed metamaterials

• Main Author: Pacheco, Joe, 1978-
• Other Authors: Jin A. Kong.
• Format: Others
• Language: English
• Published: Massachusetts Institute of Technology 2005
• Subjects: Electrical Engineering and Computer Science.
• Online Access: http://hdl.handle.net/1721.1/16615

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2004. === Vita. === Includes bibliographical references (p. 223-244). === This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections. === Materials with simultaneously negative permittivity and permeability over a certain frequency band were first studied by Veselago in 1968, who termed such media left-handed (LH) due to the LH triad formed by the electric field vector, the magnetic field vector, and the phase propagation vector. However, since no such naturally occurring materials were known, Veselago's work laid dormant for nearly 30 years. Recently though, a composite material, also known as a metamaterial, consisting of the periodic arrangement of metallic rods and split-rings has been shown to exhibit left-handed properties. Because the dimension of the rods and rings that makeup the metamaterial are small compared to the wavelength of interest, it is possible to approximately describe their bulk electromagnetic properties using an effective permittivity and an effective permeability. In this thesis, the properties and potential applications of LH media are explored. In addition, various tools are presented for the purpose of characterizing metamaterial designs. Before studying their metamaterial realization, the basic properties of propagation, radiation, and scattering through homogeneous LH media are studied. Many of the basic properties of LH media are in contrast to those typically encountered in right-handed media. For example, using a rigorous plane wave analysis of propagation and transmission into a dispersive LH medium from a RH medium, it is shown that power refracts at a negative angle, without violating causality. Second, the perfect lens concept is studied through a Green's function analysis. It is shown that under the perfect lens requirement, that a single source outside a LH media slab will generate two perfect images. === (cont.) Interestingly though, the time-averaged power flow inside the slab forms a sink. However, it is shown that while the introduction of loss eliminates this behavior, the lens becomes imperfect. It is seen that even a small amount of loss can destroy the imaging properties of the LH media lens. In terms of scattering, the Mie solution for plane wave scattering by a LH medium sphere is examined. It is shown that where applicable, care must be taken in choosing the appropriate algebraic signs of the wavenumbers in the evaluation of the Mie coefficients. In addition, it is then shown that a sphere composed of a LH medium will focus incoming energy into a spot inside the sphere. Finally, because the metamaterials studied in this thesis are anisostropic, the effects of aniostropy on reflection and transmission are examined. Next, various tools for understanding and characterizing left-handed metamaterials are presented. First, the accuracy of approximate analytic models of the rods and split-rings is investigated by using two-dimensional FD-TD simulations to compare transmission characteristics. It is shown that the rods tend to agree more favorably with their analytic model than the split-rings do. Next, in order to better understand the behavior of the rods and rings separately, numerical simulations of rods (or rings) embedded in homogeneous mag- netic (or electric) plasma media were performed. Using the transmission characteristics, it is shown that in order to obtained left-handed features, the plasma in the immediate vicinity of the rods or rings needed to be removed, ... === by Joe Pacheco, Jr. === Ph.D.