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Full-Text Articles in Engineering
Focused Beam System Biaxial Material Characterization, Nicholas A. O'Gorman
Focused Beam System Biaxial Material Characterization, Nicholas A. O'Gorman
Theses and Dissertations
Electromagnetic material characterization is the process of determining the constitutive parameters (complex permittivity and permeability) of given a sample. Due to the large number of unknowns involved, multiple unique measurements are required for material property extraction. Many measurement methods, such as waveguides and striplines, possess a rigid internal structure that the sample being measured must adhere to. This rigidity limits these methods to samples that fit within the device and inhibits oblique sample orientations, limiting the number of independent measurements that can be obtained. A focus beam system, due to being an open system with greater freedom in sample size …
Computational And Experimental Development Of 2d Anisotropic Photonic Crystal Metamaterials, James A. Ethridge
Computational And Experimental Development Of 2d Anisotropic Photonic Crystal Metamaterials, James A. Ethridge
Theses and Dissertations
The future of optical devices involves manipulation of nanoscale structure in order to achieve full control over the properties of the device. In fields as diverse as directed energy, remote sensing, optical communications and optical computing, these devices promise to greatly improve performance and efficiency. To advance this further, novel samples that incorporate both photonic crystal (PhC) structure and metamaterial properties, known as PhC metamaterials, are proposed. These PhC metamaterials allow for complete control over the directionality of the light-matter interaction to serve in these new applications. To develop this technology, first, metamaterials with no PhC structure are fabricated using …
Non-Destructive Characterization Of Rotated Uniaxial Anisotropic Materials, Alexander G. Knisely
Non-Destructive Characterization Of Rotated Uniaxial Anisotropic Materials, Alexander G. Knisely
Theses and Dissertations
Electromagnetic material characterization of anisotropic media requires measurement diversity, minimal measurement uncertainty and insight into sample symmetry. Additionally, non-destructive characterization techniques are valued over legacy measurement techniques because a destructive approach requires sample preparation to execute a measurement. A Single Port Waveguide Probe (SPWP) non-destructive material characterization technique is proposed to accommodate measuring a metal backed, known thickness, rotated uniaxial anisotropic material. A rotated uniaxial sample possesses unique transverse constitutive components and a longitudinal constitutive component which is the same as one of the transverse values. The SPWP consists of a rectangular waveguide aperture cut in the center of a …
Tunable Terahertz Metamaterials With Germanium Telluride Components, Christopher H. Kodama
Tunable Terahertz Metamaterials With Germanium Telluride Components, Christopher H. Kodama
Theses and Dissertations
Terahertz (THz) technology is an emerging field with many exciting applications. THz waves can be used to locate explosives and illicit drugs in security applications, or DNA and other molecule resonances in medical applications. THz frequencies represent the next level of modern, high-speed computing, but they also can be used for covert battlefield communications links. Metamaterials are an integral part of THz technology because they can be used to create exotic material properties—permittivities and permeabilities—in a part of the frequency spectrum that is otherwise rather empty and passive. This work aims to acquire a fuller understanding of THz metamaterials in …
Design, Fabrication And Testing Of Tunable Rf Meta-Atoms, Derrick Langley
Design, Fabrication And Testing Of Tunable Rf Meta-Atoms, Derrick Langley
Theses and Dissertations
Metamaterials are engineered structures designed to alter the propagation of electromagnetic waves incident upon the structure. The focus of this research was the effect of metamaterials on electromagnetic signals at radio frequencies. RF meta-atoms were investigated to further develop the theory, modeling, design and fabrication of metamaterials. Comparing the analytic modeling and experimental testing, the results provide a deeper understanding into metamaterials which could lead to applications for beam steering, invisibility cloaking, negative refraction, super lenses, and hyper lenses. RF meta-atoms integrated with microelectromechanical systems produce tunable meta-atoms in the 10 - 15 GHz and 1 - 4 GHz frequency …
Design, Modeling, And Measurement Of A Metamaterial Electromagnetic Field Concentrator, Noel A. Humber
Design, Modeling, And Measurement Of A Metamaterial Electromagnetic Field Concentrator, Noel A. Humber
Theses and Dissertations
This document addresses the need to improve the design process for creating an optimized metamaterial. In particular, two challenges are addressed: creating an electromagnetic concentrator and optimizing the design of metamaterial used to create the electromagnetic concentrator. The first challenge is addressed by developing an electromagnetic field concentrator from a design of concentric geometric shapes. The material forming the concentrator is derived from the application of transformation optics. The resulting anisotropic, spatially variant constitutive parameter tensors are then approximated with metamatieral inclusions using the combination of an AFIT rapid metamaterial design process and a design process created for rapid metamaterial …
Characterization And Measurement Of Passive And Active Metamaterial Devices, Christopher A. Lundell
Characterization And Measurement Of Passive And Active Metamaterial Devices, Christopher A. Lundell
Theses and Dissertations
This document addresses two major obstacles facing metamaterial development: uncertainty in the characterization of electromagnetic field behavior in metamaterial structures and the relatively small operational bandwidth of metamaterial structures. To address the first obstacle, a new method to characterize electromagnetic field behavior in a metamaterial is presented. This new method is a bistatic radar cross section (RCS) measurement technique. RCS measurements are well-suited to measuring bulk metamaterial samples because they show frequency dependence of scattering angles and offer common postprocessing techniques that can be useful for visualizing results. To address the second obstacle, this document characterizes the effectiveness of an …
Electromagnetic Field Control And Optimization Using Metamaterials, Jeffrey S. Mcguirk
Electromagnetic Field Control And Optimization Using Metamaterials, Jeffrey S. Mcguirk
Theses and Dissertations
Transformation optics has shown the ability to cloak an object from incident electromagnetic radiation is possible. However, the material parameters are inhomogeneous, anisotropic, and, in some instances, singular at various locations. In order for a cloak to be practically realized, simplified parameter sets are required. However, the simplified parameters result in a degradation in the cloaking function. Constitutive parameters for simplified two-dimensional cylindrical cloaks have been developed with two material property constraints. It was initially believed satisfying these two constraints would result in the simplified cylindrical cloaks having the same wave equation as an ideal cloak. Because of this error, …