UNIVERSITY OF UTAH
ELECTRICAL AND COMPUTER ENGINEERING DEPARTMENT
DISSERTATION DEFENSE FOR THE DEGREE OF
DOCTOR OF PHILOSOPHY
Advisor: David Schurig
Metamaterials and their Applications in Imaging
Microwave/millimeter-wave imaging systems have become ubiquitous and have found applications in areas like astronomy, bio-medical diagnostics, remote sensing, and security surveillance. These areas have so far relied on conventional imaging devices (employing Nyquist principles) which at best can provide diffraction-limited images. With the advent of metamaterials, unique and extraordinary electromagnetic responses can be achieved which can potentially revolutionize imaging devices. Such extraordinary responses include: negative refraction, strong anisotropy, gradient-index response, perfect absorption, magneto-electric effects (chirality), and many more. When adopted into imaging devices, these response characteristics could potentially: beat diffraction-limits, improve imaging performance or lead to unprecedented control over light propagation. Along with metamaterials, mathematical tools like transformation optics or torsion optics (which leverages Riemannian geometry under the geometrical optics limit) facilitate the design and development of systems with exclusive effects such as invisibility cloaking, perfect and/or aberration-free lensing, near-field magnification, and total control of the polarization field. When metamaterial devices are combined with computational imaging techniques, the resulting systems can exploit apriori information to reach previously unattainable trade-off positions in the space of: image quality, size, weight, power and cost. In this dissertation we present and discuss metamaterial based imaging devices, and associated principles and techniques that achieve such enhanced imaging performance (See Fig.0.1).
In Chapters. [1 & 2], we present a novel “medium-as-device” approach to experimentally demonstrate a metamaterial, perfect-absorber-based focal plane array. The microwave focal plane array was demonstrated both as an intensity detector and as a vector signal detector. The former setup was used to perform interferometric direction finding of RF emitters.
In Chapter. , we present a transformation optics designed near-field magnifier, for sub-wavelength imaging. We discuss and present various design parameters and trade-offs associated with such magnifiers. We adopt grid relaxation techniques that result in material properties that are more amenable to implementation. In Chapter. , we present a novel “Torsion Optics” design method, leveraging Riemannian geometric concepts, which facilitates the design of devices with gradient chiral material properties, giving an unprecedented control over the polarization field.
In Chapter. , we demonstrate a prototype W-band (75 -110 GHz) sparse, syntheticaperture, computational imaging system that leverages intrinsic frequency diversity in the sparse aperture. We also formulate an information-based metric to evaluate the performance of a given image transfer matrix for noise-limited, computational imaging systems. In Chapter. , we describe a computationally-fast approach for propagation of vector electromagnetic fields through an axi-symmetric medium (such as a lens) using cylindrical harmonic decomposition techniques. The motivating application is to computational imaging systems, where the forward propagation model must be computed quickly, for real time results. This approach was also applied in the near-field magnifier design and analysis.
In Chapter. , as a part of future directions, we exploit all of the above approaches to propose a multi-functional RF system leveraging commercial off-the-shelf integrated circuits. We propose to investigate, in particular, the synergies that result when a single hardware platform can support: focusing-optic-free computational imaging, satellite links on mobile platforms, and electronic targeting of non-lethal force.
Wednesday October 26, 2016
9:30 AM, ECE conference room
Merrill Engineering Building (MEB) room 2109
The public is invited