Dissertation/Thesis Abstract

Theory, Characterization and Applications of Infrared Hyperbolic Metamaterials
by Fullager, Daniel B., Ph.D., The University of North Carolina at Charlotte, 2017, 101; 10267303
Abstract (Summary)

Hyperbolic Metamaterials (HMMs) are engineered structures capable of supporting lightmatter interactions that are not normally observed in naturally occuring material systems. These unusual responses are enabled by an enhancement of the photonic density of states (PDOS) in the material. The PDOS enhancement is a result of deliberately introduced anisotropy via a permittivity sign-change in HMM structures which increases the number and frequency spread of possible wave vectors that propagate in the material. Subwavelength structural features allow effective medium theories to be invoked to construct the k-space isofrequency quadratic curves that, for HMMs, result in the k-space isofrequency contour transitioning from being a bounded surface to an unbounded one. Since the PDOS is the integral of the differential volume between k-space contours, unbounded manifolds lead to the implication of an infinite or otherwise drastically enhanced PDOS. Since stored heat can be thought of as a set of non-radiative electromagnetic modes, in this dissertation we demonstrate that HMMs provide an ideal platform to attempt to modify the thermal/IR emissivity of a material. We also show that HMMs provide a platform for broadband plasmonic sensing. The advent of commercial two photon polymerization tools has enabled the rapid production of nano- and microstructures which can be used as scaffolds for directive infrared scatterers. We describe how such directive components can be used to address thermal management needs in vacuum environments in order to maximize radiative thermal transfer. In this context, the fundamental limitations of enhanced spon- taneous emission due to conjugate impedance matched scatterers are also explored. The HMM/conjugate scatterer system’s performance is strongly correlated with the dielectric function of the negative permittivity component of the HMM. In order to fully understand the significance of these engineered materials, we examine in detail the electromagnetic response of one ternary material system, aluminium-doped zinc oxide (AZO), whose tuneable plasma frequency makes it ideal for HMM and thermal transfer applications. This study draws upon first principle calculations from the open literature utilizing a Hubbard-U corrected model for the non-local interaction of charge carriers in AZO crystalline systems. We present the first complete dielectric function of industrially produced AZO samples from DC to 30,000 cm –1 and conclude with an assessment of this material’s suitability fo the applications described.

Indexing (document details)
Advisor: Fiddy, Michael A.
Commitee: Adams, Ryan S., Boreman, Glenn D., Her, Tsing-Hua, Stokes, Edward B.
School: The University of North Carolina at Charlotte
Department: Optical Science and Engineering
School Location: United States -- North Carolina
Source: DAI-B 78/09(E), Dissertation Abstracts International
Subjects: Engineering, Theoretical physics, Materials science
Keywords: Evanescent field metamaterial, Hyperbolic metamaterials, Sub wavelength gratings, Thermal metamaterials
Publication Number: 10267303
ISBN: 9781369702514
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