Metamaterial enhanced coupling

In the past decade interest in metamaterials has risen dramatically. This is due, in large part, to metamaterials' ability to exhibit electromagnetic behavior not normally found in nature. This is because these artificial structures display a strong electromagnetic response as a result of their geometry, as opposed to their chemistry, and that response typically dominates that of the substrate they are placed on. As a result, metamaterials can couple free space radiation in previously unheard of ways, and in this thesis I examine several of these coupling mechanisms. After an appropriate discussion of theoretical and experimental tools required for metamaterial study, the thesis turns to the metamaterial substrate and explores the coupling effects of the metamaterial and the substrate itself. We discuss the theory and experimentally demonstrate that the metamaterial and substrate composite can couple free space radiation for use in enhanced dielectric sensing, perfect absorption, and even mechanical deflection for electromagnetic detection. In addition to coupling with dielectric materials, the near field response of a metamaterial can also couple with another metamaterial. Subsequently, this thesis investigates the coupling between a pair of identical split ring resonators, and develops a general framework for evaluating the mode hybridization that results from their near field interaction. In fact, we find that the near field coupling is extremely sensitive to the relative orientation of the two metamaterials, and results in mode splitting between the two resonators. By manipulating their lateral displacement, the coupling, and the mode splitting, can be altered. In this way, an unprecedented modulation of the metamaterial response is demonstrated. Finally, we turn our attention to the effects that metamaterial behavior has on the far field response. Specifically, we focus on the symmetry, or lack thereof, of the unit cell and show that it manifests itself as a birefringence in the far field. As a result, metamaterials can be used as wave retarders to couple between polarization states. Herein we analyze this behavior and experimentally demonstrate functioning metamaterial based terahertz waveplates that are highly efficient at a previously unachieved sub wavelength size.

Grantor dc:publisher

Boston University

Year dc:date.issued

2012

Author dc:creator

• Strikwerda, Andrew

Language dc:language.iso

en_US

Handle dc:identifier.uri

https://hdl.handle.net/2144/31611

OAI identifier oai:identifier

oai:open.bu.edu:2144/31611