Electronic Theses and Dissertations

Title

Homogenization of Structured Metasurfaces and Uniaxial Wire Medium Metamaterials for Microwave Applications

Date of Award

2012

Document Type

Dissertation

Degree Name

Ph.D. in Engineering Science

First Advisor

Alexander B. Yakovlev

Second Advisor

William Staton

Third Advisor

Atef Z. Elsherbeni

Abstract

In recent years, the study of electromagnetic wave interaction with artificial media has been the subject of intense research interest due to their extraordinary properties such as negative refraction, partial focusing, enhanced transmission, and spatial filtering, among others. Artificial media are crystals of various periodic metallic inclusions with dimensions of the order of ?/10 - ?/4. When compared to natural materials, the inclusions are, thus, not as small in terms of the wavelength, even in the optical band. Therefore, one should expect the electrodynamics of these media to be inherently non-local, characterized by strong spatial dispersion effects. The dissertation includes two parts and focuses on the electromagnetic wave propagation in metamaterials formed by stacked metasurfaces and structured wire media. In the first part, we propose physical systems that mimic the observed behavior of stacked metal-dielectric layers at optical frequencies, but in the microwave region of the spectrum using stacked metascreens, and at low-THz using graphene-dielectric stack. The analysis is carried out using simple analytical circuit model or transfer matrix method with the homogenized impedance for the metasurfaces. The physical mechanisms of the observed behavior is clearly explained in terms of the open/coupled Fabry-Pérot resonators. The methodology can be useful in the design of wideband planar filters based on these metasurfaces with a specific response. The second part focuses on the development of homogenization models for wire medium loaded with arbitrary impedance insertions and metallic patches, to characterize negative refraction, partial focusing, and subwavelength imaging. We propose a new concept of suppressing the spatial dispersion effects in the wire media by employing lumped inductive loads. Based on the proposed concept, we demonstrate an ultra-thin structure which exhibits indefinite dielectric response, all-angle negative refraction and high transmission. Also compact electromagnetic band-gap structure with a huge stopband for surface-wave propagation is presented, which finds application in antenna technology. Partial focusing of electromagnetic radiation at microwave frequencies from a thick wire medium slab with periodic impedance loadings is detailed. Numerical simulation and homogenization results are presented in good agreement. Finally, the subwavelength imaging using wire medium with impedance loadings is demonstrated.

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