<p>Metamaterials have gained extensive attention in recent years due to their ability to exhibit material properties otherwise difficult or impossible to obtain using natural materials. Nonlinear and active metamaterials in particular exhibit great promise for exploring new effects and applications, from tunability to mixing. However, nonlinear and active metamaterials have been explored significantly less than linear metamaterials to this point and much work has focused on the fundamental physics of nonlinear metamaterials. Our aim is to further extend the knowledge of practical nonlinear metamaterials and to demonstrate how they can be transformed to real-world applications through the use of embedded devices. In this dissertation, we demonstrate a variety of ways that devices can be embedded within metamaterial unit cells to provide nonlinear and active effects. </p><p>Chapter 1 introduces the basic theory of metamaterials, background of existing work, and the current limitations of nonlinear and active metamaterial design. In Chapter 2, we present the design, simulation, fabrication, and verification of an RF limiter metamaterial. We show how a metamaterial can be designed using RF engineering principles to act as an effective limiter in a new topology, relying on nonlinear devices embedded within a metamaterial. Chapter 3 shows our design and demonstration of a power harvesting metamaterial. We design a nonlinear metamaterial towards a potential application, discussing how the selection of an appropriate embedded device provides our desired functionality. In Chapter 4 we show how nonlinear and active metamaterials can be used to realize phase conjugation, including demonstration of negative refraction and imaging through the use of these metamaterials. We also discuss design approaches to moving these metamaterials towards real-world applications. Chapter 5 discusses our work concerning metamaterials based on transistors. First we show that appropriate design of a transistor circuit allows us to tune the quality factor and resonant frequency of a metamaterial. We use this metamaterial for time-varying mixing, as well, demonstrating a mixing metamaterial that remains linear. We then illustrate how using transistors as nonlinear devices provides much greater design freedom for use with metamaterials. We show that the nonlinearity of a metamaterial can be dramatically enhanced through the use of transistors and even dynamically tuned, applying these nonlinear metamaterials to applications including phase conjugation and acoustoelectromagnetic modulation. In Chapter 6 we summarize the achievements of the presented research and directions for future work that build on the work described in this thesis.</p> / Dissertation
| Identifer | oai:union.ndltd.org:DUKE/oai:dukespace.lib.duke.edu:10161/8668 |
| Date | January 2014 |
| Creators | Katko, Alexander Remley |
| Contributors | Cummer, Steven A |
| Source Sets | Duke University |
| Detected Language | English |
| Type | Dissertation |
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