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Title: Surface waves in magnetic metamaterials : phenomena and applications
Author: Hadjicosti, Krystallo
ISNI:       0000 0004 6421 0373
Awarding Body: Imperial College London
Current Institution: Imperial College London
Date of Award: 2017
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Surface waves in metamaterials are responsible for a range of phenomena, and understanding their properties is essential for the development of metamaterial applications. This thesis first investigates the propagation of surface magneto-inductive waves along a defect in an array of split-ring resonators. A new approach is demonstrated in which the defect is formed by changing the resonant frequency of the defect elements. The dispersion relation was derived and its dependence on the sign and the strength of the inter-element coupling and the relationship between the resonant frequencies was studied. Waveguides, couplers and filters were simulated, and the theoretical results were verified experimentally. The thesis further investigates the effect of inter-element coupling on surface magneto-inductive polaritons. Using two models, one relying on the effective-medium approximation and the other on equivalent circuits, we studied theoretically surface polaritons propagating along an interface between air and a magnetic metamaterial. With a moderate longitudinal coupling, a single polariton is supported similar to the un-coupled case. However, the presence of a transverse coupling changed the polariton dispersion dramatically. The effective-medium model yielded two branches of polariton dispersion at low values of transverse coupling. As the coupling increased, both polaritons disappeared. The validity of the effective-medium model was further tested by employing the circuit model. In this model, surface polaritons could exist in the presence of a transverse coupling only if the boundary layer of the metamaterial included additional impedances, which could become non-Foster circuits. The results reveal that the inter-element coupling is a major mechanism affecting the properties of the polaritons. They also highlight the limitations of using bulk effective-medium parameters for interface problems in metamaterials.
Supervisor: Sydoruk, Oleksiy ; Maier, Stefan Sponsor: Leverhulme Trust
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral