Browsing by Subject "Metamaterial"
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Item Asymmetric scattering in elastic waveguides with applications to nondestructive evaluation and acoustic metamaterials(2023-12) Parker, Samuel David; Haberman, Michael R. (Michael Richard), 1977-; Hamilton, Mark F; Roettgen, Daniel R; Salamone, Salvatore; Wilson, Preston SAsymmetric scattering in waveguides is a behavior in which the field scattered from a discontinuity is dependent on the direction of incidence. The existence of multiple propagating modes in waveguide systems like plates and beams provides a platform to explore asymmetric scattering through direction-dependent mode coupling and asymmetric absorption. While asymmetric scattering is a well-known behavior, the physical conditions required to produce the behavior are not well-understood, hindering its use for design of engineered materials and for novel nondestructive evaluation techniques. This work investigates asymmetric scattering and its applications to nondestructive evaluation (NDE) techniques and design of acoustic and elastic metamaterials (AMM). First, a pump-probe technique called Dynamic Asymmetric Transmission Measurement (DATM) is developed for use with elastic beams to detect and classify damage that is has stress-dependent scattering behavior. When subjected to a time-harmonic background stress field, local nonlinearities like surface-breaking cracks display a scattering behavior that is asymmetric with respect to the oscillatory phase of the background stress field. The method utilizes mode conversion between the fundamental symmetric and antisymmetric Lamb modes to capture the variation in scattering response with the background stress field. The method is demonstrated on elastic beams with localized damage and provides an enhanced ability to classify damage compared to existing NDE techniques. Next, constraints on asymmetric scattering imposed by reciprocity and passivity were investigated theoretically to understand implications on scatterer properties with application to NDE techniques like DATM and ultrasonic inspection as well as to inform design considerations for AMM applications. In a multi-modal Lamb wave system, reciprocity was shown to relate various Lamb wave scattering parameters for reflection and transmission, respectively. Combined with symmetry arguments and consideration of passivity, necessary conditions to produce asymmetric scattering and asymmetric absorption were developed. These conditions were verified through numerical studies, with applications to novel NDE techniques and AMM design. Finally, a scatterer that is geometrically asymmetric and resonant was then investigated with applications to Willis materials, a class of homogenized materials that has constitutive relationships of stress and momentum that are a function both strain and velocity. Simulations showed that the scatterer displayed strongly asymmetric mode coupling when excited with the fundamental symmetric and antisymmetric Lamb modes. The scatterer is then modeled using reduced-order beam theories, incorporating necessary Willis coupling coefficients to derive constitutive relationships. An effective material property extraction technique is proposed and demonstrated numerically to determine the effective properties of the scatterer as defined in the constitutive relationships.Item Coextrusion : a feasible method to manufacture negative stiffness inclusions(2013-08) Hook, Daniel Taylor; Kovar, DesiderioThis work demonstrates the effectiveness of coextrusion as a method to manufacture negative stiffness inclusions for use in vibrational damping applications. The theory and mechanics of negative stiffness and coextrusion are introduced and the process of creating and extruding a feed rod with negative stiffness architecture explained. Coextrusion is shown to be a viable method to create negative stiffness inclusionsItem Design and analysis of an underwater leaky wave antenna(2021-05-07) Broadman, Craig Wing; Haberman, Michael R. (Michael Richard), 1977-Acoustic imaging in water traditionally relies on phased arrays of active electro-acoustic transducers to steer acoustic energy in specific directions. Prevalent in ships, submarines, and autonomous underwater vehicles (AUVs), phased arrays are high in weight and processing power. One potential alternative approach to steer acoustic beams is to use a single transducer attached to a dispersive antenna that radiates or receives acoustic energy from different directions as the frequency of operation changes. This is known as a leaky wave antenna (LWA). While LWAs have been proven effective in beam steering for electromagnetic and air-borne acoustic waves, the design of an analog device in water presents a unique challenge due to the low contrast in acoustic impedance between elastic solids and water, which necessitates the consideration of fluid-elastic coupling in the design of the elastic LWA. This work presents an approach to design an elastic metamaterial waveguide coupled to an external fluid domain as one means to create an acoustic LWA for underwater operation.Item Fano-resonant plasmonic metamaterials and their applications(2012-08) Wu, Chihhui; Shvets, G.; Shih, Chih-Kang; Demkov, Alex; Li, Xiaoqin; Alu, AndreaManipulating electromagnetic fields with plasmonic nanostructures has attracted researchers from interdisciplinary areas and opened up a wide variety of applications. Despite the intriguing aspect of inducing unusual optical properties such as negative indices and indefinite permittivity and permeability, engineered plasmonic nanostructures are also capable of concentrating electromagnetic waves into a diffraction-unlimited volume, thus induce incredible light-matter interaction. In this dissertation, I’ll discuss about a class of plasmonic structures that exhibit the Fano resonance. The Fano resonance is in principle the interference between two resonant modes of distinct lifetimes. Through the Fano resonance, the electromagnetic energy can be trapped in the so called “dark” mode and induce strong local field enhancement. A variety of Fano resonant nanostructures ranging from periodic planar arrays to simple clusters composed of only two particles are demonstrated in this dissertation. By artificially designing the dimensions of the structures, these Fano-resonant materials can be operated over a broad frequency range (from visible to mid-IR) to target the specific applications of interest. In this dissertation, I’ll show the following research results obtained during my PhD study: (1) the double-continuum Fano resonant materials that can slow down the speed of light over a broad frequency range with little group velocity dispersion. (2) Ultra-sensitive detection and characterization of proteins using the strong light-matter interaction provided by the Fano-reonant asymmetric metamaterials. (3) Metamaterials absorbers with nearly 100 % absorbance, tunable spectral position, expandable bandwidth, and wide angle absorption. These Fano-resonant materials can have profound influences in the areas of optical signal processing, life science, bio-defense, energy harvesting and so on.Item Fano-resonant plasmonic metasurface for cancer detection using few-cell spectroscopy and other optical applications in mid-infrared(2016-06-10) Arju, Nihal; Shvets, G.; Alu, Andrea; Florin, Ernst-Ludwig; Li, Xiaoqin; Sokolov, KonstantinThe field of metamaterials holds enormous promise in our ability to engineer artificial (‘meta’) material to suit a wide variety of needs. Metamaterials have been designed to achieve electromagnetic cloaking, negative refractive index, perfect absorption and many other phenomena that were thought to be impossible to achieve. Fano resonant metamaterials form a subclass of metamaterials that possess one or more Fano-type resonances. The Fano resonance arises out of interference between two resonance modes with disparate lifetimes. A variety of Fano resonant asymmetric metamaterials (FRAMMs) have been investigated in this dissertation. A circularly dichroic double continuum FRAMM was constructed and the effect of tuning the interference between modes on a Fano resonance has been examined. These metamaterial surfaces (metasurfaces) have strong field confinement. As a result, a small change in the near vicinity of the metasurface creates a detectable change in the metasurface response, which allows the metasurfaces to be used as sensors. The FRAMM was used to detect monolayer of protein otherwise undetectable using Fluorescence microscopy. It was also used to examine different cell types. One promising strategy for early cancer detection involves detecting cancerous cells in the bloodstream. These circulating tumor cells (CTCs) spread through the body and create tumors. Metasurface sensors may be used to conduct spectroscopy on cells in order to spectroscopically identify different cell types, including whether the cells are cancerous or not. A statistical analysis reveals that it is possible to detect different cell types using metasurfaces.Item Homogenization of metamaterials with spatial dispersion(2011-08) Fietz, Christopher Robin; Shvets, G.; Fink, Manfred; Shih, Chih-Kang; Chelikowsky, James; Ling, HaoA study is made of the problem of metamaterial homogenization, which is the attempt to represent an artificially fabricated inhomogeneous periodic structure as a homogeneous medium with an electromagnetic response described by a number of constitutive parameters (permittivity, permability, etc.) In particular, the importance of spatial dispersion in metamaterials and the need to characterize metamaterials with wavevector dependent constitutive parameters is explained an examined. A brief survey of important previous attempts at metamaterial homogenization is presented. This is followed by a discussion of spatial dispersion in metamaterial crystals. The importance of spatial dispersion in metamaterials is justified and some manifestations of spatial dispersion described. In particular the little known phenomenon of bianisotropy in centrosymmetric crystals due to spatial dispersion is explained. Also, the effects of spatial dispersion on physical quantities such as energy flux and dissipation are identified. We then describe a new method for solving for the free eigenmodes of a metamaterial crystal with a complex wavevector eigenvalue simulation. Next, two different theoretical attempts by the author at metamaterial homogenization are described, both accompanied by tests of the calculated constitutive parameters and critical examination of the strengths and weaknesses of each approach. Finally, strong evidence of the presence and importance of spatial dispersion in metamaterials is presented.Item Inverse design of metamaterials for wave control(2020-05-11) Goh, Heedong; Kallivokas, Loukas F.; Alù, Andrea; Cox, Brady; Haberman, Michael R.; Hamilton , Mark F.; Manuel, LanceMetamaterials are engineered materials, whose spatially periodic arrangement of their constituent materials endows the composite assembly with rather unconventional properties, when macroscopically observed. In the context of the three wave-supporting physics regimes -elastodynamics, acoustics, and electromagnetics- metamaterials present unique opportunities for previously unimaginable user control over the resulting wave behavior. To date, the design of metamaterials is mostly done on an ad hoc basis, relying mostly on one-of-a-kind or incremental physical experiments and forward computational modeling. This dissertation introduces a systematic methodology, rooted in inverse problem theory, for engineering the dispersive properties of periodic media to meet a priori, user-defined, wave control objectives. Both scalar and vector waves are considered. In the developed methodology, the material properties and geometry parameters of the unit cell of the periodic medium become the inversion variables. The inversion is driven by the user-defined wave control objective, constrained by the dispersive characteristics of the unit cell. Though the methodology is flexible enough and can accommodate fairly broad dispersion engineering objectives, here the focus is on band-gaping propagating waves at user-defined frequency ranges. Numerical results in the frequency domain demonstrate that the inversion process yields unit cells that indeed attain the user-defined dispersive behavior. The inverted-for unit cells are then used to build metamaterial assemblies of not only finite periodicity, as opposed to infinite, but of fairly narrow periodicity, and are tested in the time domain against broadband excitations: it is shown that it is possible to attain the desired wave control with sub-wavelength size metamaterial assemblies.Item Material property extraction procedure for electromomentum coupled metamaterials(2023-08) Casali, Matthew A.; Haberman, Michael R. (Michael Richard), 1977-Electromomentum (Eμ) coupling is a material response that couples the macroscopically observable time-varying electric field to the momentum of the material. This unique behavior has been shown theoretically to result from dynamics at subwavelength length-scales due to asymmetries in heterogeneous piezoelectric materials. Electromomentum coupling is of interest to the engineering and scientific community for its ability to simultaneously sense both the acoustic pressure and particle velocity at a single point in space, thus enabling the creation of vector sensor devices using a single material. This thesis presents a study of the characterization of this novel transduction behavior through multiscale models and numerical experiments. The material models include analytical and finite element methods that extend the work of Pernas-Salomón et al. [Wave Motion, 106, 102797, (2021)]. The models simultaneously provide insight into the subwavelength behavior that leads to Eμ coupling on the macroscopic scale as well as metrics of the coupling strength. Additionally, these models are employed in a design strategy to maximize Eμ coupling demonstrated by a heterogeneous piezoelectric scatterer using readily available materials and easily manufactured geometries. To achieve this, a series of candidate designs are modeled and their Willis and/or Eμ coupling is quantified. The models are then employed to design an experimental method to characterize Eμ coupling of a sample using a water-filled impedance tube. The impedance tube measurement procedure presented in this work is a generalization of existing methods used to infer the frequency-dependent material properties of a sample from measurements of its scattering coefficients and associated property extraction algorithms. Namely, the works of Song and Bolton to measure the complex impedance and wavenumber or phase speed and attenuation [J. Acoust. Soc. Am., 107(3), pp. 1131-1152, (2000)], Fokin et al. to measure the complex-valued density and bulk modulus, including negative values, [Phys. Rev. B, 76(14), 114302, (2007)], and Muhlestein et al. who extended the work of Fokin et al. to measure Willis coupling in addition to density and bulk modulus [Nat. Commun., 8, 15625, (2017)]. This work also considers practical details such as dispersion, hydrophone calibration, and sample mounting, that are specific to measurements in a water-filled impedance tube and their influence on the accuracy of measurements of scattering coefficients using this apparatus, ending with recommendations for future measurements.Item Metamaterial window glass for adaptable energy efficiency(2014-05) Mann, Tyler Pearce; Ezekoye, Ofodike A.; Howell, John R.A computational analysis of a metamaterial window design is presented for the purpose of increasing the energy efficiency of buildings in seasonal or cold climates. Commercial low-emissivity windows use nanometer-scale Ag films to reflect infrared energy, while retaining most transmission of optical wavelengths for functionality. An opportunity exists to further increase efficiency through a variable emissivity implementation of Ag thin-film structures. 3-D finite-difference time-domain simulations predict non-linear absorption of near-infrared energy, providing the means to capture a substantial portion of solar energy during cold periods. The effect of various configuration parameters is quantified, with prediction of the net sustainability advantage. Metamaterial window glass technology can be realized as a modification to current, commercial low-emissivity windows through the application of nano-manufactured films, creating the opportunity for both new and after-market sustainable construction.Item Metamaterials with broken symmetry and their applications(2018-05-01) Sun, Liuyang; Li, Elaine; Shih, Chih-Kang; Shvets, Gennady; Lai, Keji; Wang, ZhengConventionally, the development of optical technology has often relied on the discovery of new natural materials with desirable optical properties for specific tasks, e.g. birefringence for polarizer, or fluorite for dispersionless lens. Meanwhile, the typical feature dimensions of the optical components are much larger than the wavelength of light. For example, the radius of a curved lens surface is on the order of centimeters. Recently, instead of ‘discovering’ new materials with proper optical properties, great efforts have been dedicated to ‘designing’ artificial materials of desirable optical properties. Such artificial materials are known as metamaterials, which are made from assemblies of chosen dielectric and/or metallic components. Optical metamaterials have anomalous optical properties beyond what are naturally available in their basic constituent materials, e.g., optical magnetism and negative refractive index. With advanced nano fabrication and imaging technologies, researchers are able to make metamaterials in unprecedented ways. New designs and applications of metamaterials are being developed at rapid pace. However, challenges remain in various aspects. For example, mechanisms underlying the novel properties of complicated metamaterials are not understood thoroughly. How can one converge to effective designs of metamaterials while facing an enormous parameter space. In this thesis, we explore intentional symmetry breaking as a guiding principle for designing metamaterials. We experimentally demonstrate their properties and applications. In the first example, we first theoretically explore the light-matter interaction for a single metal nanoparticle (NP) and metamolecules which are clusters of NPs. The NPs can be assembled in such a way that they exhibit strong magnetic response at optical frequencies, a property absent in natural materials. While enhancement of the optical magnetism has previously been demonstrated by breaking the symmetry of the metamolecule, a fundamental understanding of the mechanisms is lacking. By fabricating the metamolecule of suitably designed broken symmetries, we separated the magnetic moment and magneto-electric contributions to the magnetic resonance in the optical frequency regime for the first time. By choosing uniform and spherical NPs, and by using angle- and polarization-resolved scattering measurements, we separate the different contributions to optical magnetism. The demonstrated capability of controlling different contributions to the magnetic resonance is expected to stimulate future development of metamolecules and metamaterials with exotic optical properties. As the second example, we designed and fabricated metasurfaces with a broken mirror symmetry. We succeeded in applying such metasurface to manipulate the valley degree of freedom in monolayer transition metal dichalcogenides (TMDCs). Valley refers to the energy extrema points in the energy bands. Typically, valley does not coupling to any external field specifically. By coupling to surface plasmon polaritons along asymmetric grooves on a metasurface, valley excitons in monolayer MoS2are spatially separated at room temperature an important step toward valleytronic applications. The combination of metasurfaces and 2D materials enables conceptually novel hybrid photonic devices that may be used to control exciton/spin/valley transport in unprecedented ways and to engineer quantum light emitters. We also demonstrated a molecule chirality sensor with zeptomole detection sensitivity based on two coupled metasurfaces lacking reflection symmetry. Chirality of biomedical molecule is strongly related to their pharmacological effects, such as potency and toxicity. We exploited the interaction between enantiomers and metamaterials with specifically designed symmetry. By placing the specimen onto a chiral metamaterial, we found that the molecular chiral signal can be enhanced by a factor of 100. The spectra obtained from enantiomers of opposite handedness show opposite spectral bending, providing a way to reveal the molecular chirality. This work presents a novel method for advanced biomedical detection with ultrathin planarized nanophotonic device. In conclusion, we have been able to theoretically analyze and experimentally realize and characterize asymmetric metamaterials to explore both fundamental physics and practical applications, oftentimes guided by symmetry considerations. We briefly discuss remaining challenges in the plasmonic metamaterial fields and possible solutionsItem Multiple-grid adaptive integral method for general multi-region problems(2011-08) Wu, Mingfeng; Yilmaz, Ali E.; Ling, Hao; Pearce, John; Alu, Andrea; Ying, LexingEfficient electromagnetic solvers based on surface integral equations (SIEs) are developed for the analysis of scattering from large-scale and complex composite structures that consist of piecewise homogeneous magnetodielectric and perfect electrically/magnetically conducting (PEC/PMC) regions. First, a multiple-grid extension of the adaptive integral method (AIM) is presented for multi-region problems. The proposed method accelerates the iterative method-of-moments solution of the pertinent SIEs by employing multiple auxiliary Cartesian grids: If the structure of interest is composed of K homogeneous regions, it introduces K different auxiliary grids. It uses the k^{th} auxiliary grid first to determine near-zones for the basis functions and then to execute AIM projection/anterpolation, propagation, interpolation, and near-zone pre-correction stages in the k^{th} region. Thus, the AIM stages are executed a total of K times using different grids and different groups of basis functions. The proposed multiple-grid AIM scheme requires a total of O(N^{nz,near}+sum({N_k}^Clog{N_k}^C)) operations per iteration, where N^{nz,near} denotes the total number of near-zone interactions in all regions and {N_k}^C denotes the number of nodes of the k^{th} Cartesian grid. Numerical results validate the method’s accuracy and reduced complexity for large-scale canonical structures with large numbers of regions (up to 10^6 degrees of freedom and 10^3 regions). Then, a Green function modification approach and a scheme of Hankel- to Teoplitz-matrix conversions are efficiently incorporated to the multiple-grid AIM method to account for a PEC/PMC plane. Theoretical analysis and numerical examples show that, compared to a brute-force imaging scheme, the Green function modification approach reduces the simulation time and memory requirement by a factor of (almost) two or larger if the structure of interest is terminated on or resides above the plane, respectively. In addition, the SIEs are extended to cover structures composed of metamaterial regions, PEC regions, and PEC-material junctions. Moreover, recently introduced well-conditioned SIEs are adopted to achieve faster iterative solver convergence. Comprehensive numerical tests are performed to evaluate the accuracy, computational complexity, and convergence of the novel formulation which is shown to significantly reduce the number of iterations and the overall computational work. Lastly, the efficiency and capabilities of the proposed solvers are demonstrated by solving complex scattering problems, specifically those pertinent to analysis of wave propagation in natural forested environments, the design of metamaterials, and the application of metamaterials to radar cross section reduction.Item Surface wave manipulation with polar dielectric thin films and topological photonic system(2018-06-18) Lai, Kueifu; Shih, Chih-Kang; Shvets, G.; Florin, Ernst-Ludwig; Fiete, Gregory; Belkin, MikhailDifferent from the well-studied wave propagation in the bulk where a plane wave extending to infinite is often conceived, the surface wave exists in the boundary defined by domains of distinct medium is well-confined with exponentially decaying tails away from this interface. This tightly-localized nature grants us enormous capability to manipulate the wave transport by tailoring the property of the interfaces and further enables various functionality for practical application. In this dissertation, a charged particle accelerator based on the surface phonon polaritons on the polar dielectric (silicon carbide) thin film is demonstrated to withstand high energy laser power and holds the promise of ultra-high accelerating gradiant in future experimental realization. The framework of wave propagation is then expanded beyond the homogenized medium to crystals with discrete periodicity which is referred as photonic crystals. The Bloch wave construct predicts that the topological insulator, a novel phenomenon in solid state physics, can be emulated by exquisite design of photonic system. Consequently, the surface waves (or edge states) between two topologically distinct photonic crystals exhibit robust and defect-immune wave transport which facilitates wide variety of applications. In particular, the RF delay line, polarized wave sorting, and two-beam accelerator based on the photonic topological insulator are investigated.