Computational simulation and realization of three-dimensional metamaterials with various exotic properties

İbili, Hande
In this study, computational analysis and realization of three-dimensional metamaterial structures that induce negative and zero permittivity and/or permeability values in their host environment, as well as plasmonic nanoparticles that are used to design metamaterials at optical frequencies are presented. All these electromagnetic problems are challenging since effective material properties become negative/zero, while numerical solvers are commonly developed for ordinary positive parameters. In real life, three-dimensional metamaterial structures, involving split-ring resonators (SRR), thin wires, and similar subwavelength elements, are designed to exhibit single negativity (imaginary refractive index) and double negativity (negative refractive index) behaviors. However, metamaterial elements have small details with respect to wavelength and they operate when they resonate. Then, their numerical models lead to large matrix equations that are also ill-conditioned, making their solutions extremely difficult, if not impossible. If performed accurately, homogenization simplifies the analysis of metamaterials, while new challenges arise due to extreme parameters. For example, a combination of zero-index (ZI) and near-zero-index (NZI) materials with ordinary media (metals, free space, etc.) results in a high-contrast problem, and numerical instabilities occur particularly due to huge values of wavelength. Similar difficulties arise when considering the plasmonic effects of metals at optical frequencies since they must be modeled as penetrable bodies with negative real permittivity, leading to imaginary index values. Different surface-integral-equation (SIE) formulations and broadband multilevel fast multipole algorithm (MLFMA) implementations are extensively tested for accurate and efficient numerical solutions of ZI, NZI, imaginary-index, and negative-index materials. In addition to their computational simulations, metamaterial designs are fabricated with a low-cost inkjet-printing setup, which is based on using conventional printers that are modified and loaded with silver-based inks. Measurements demonstrate the feasibility of fabricating very low-cost three-dimensional metamaterials using simple inkjet printing.


Full-Wave Computational Analysis of Optical Chiral Metamaterials
Guler, Sadri; Solak, Birol; Gür, Uğur Meriç; Ergül, Özgür Salih (2017-09-27)
We present computational analysis of optical chiral metamaterials that consist of helical metallic elements. At optical frequencies, metals are modeled as penetrable objects with plasmonic properties. A rigorous implementation based on boundary element methods and the multilevel fast multipole algorithm is used for efficient and accurate analysis of three-dimensional structures. Numerical results demonstrate interesting polarization-rotating characteristics of such arrays with helical elements, as well as t...
Computational Design of Optical Couplers for Bended Nanowire Transmission Lines
Tuncyurek, Yunus Emre; Karaosmanoglu, Bariscan; Ergül, Özgür Salih (2017-07-01)
We present computational analysis, optimization, and design of optical couplers that can be useful to improve the transmission along bended nanowires. After demonstrating the deteriorated energy transmission due to sharp bends, which lead to out-of-phase nanowires and diffraction, we use a rigorous simulation environment to design efficient couplers made of spherical particles. For this purpose, an optimization module based on genetic algorithms is combined with the multilevel fast multipole algorithm, lead...
Accuracy of the Surface Integral-equation Formulations for Large Negative Permittivity Values
Karaosmanoglu, B.; Ergül, Özgür Salih (2017-05-25)
Computational solutions of plasmonic problems involving metals at optical frequencies formulated with surface integral equations are considered. Numerical inaccuracies arise when using the conventional formulations for penetrable bodies, especially as the negative real permittivity becomes very large at the lower frequencies of the optical spectrum. In order to close the gap between plasmonic and perfectly conducting simulations, it is required to extend the applicability of surface integral equations to in...
Multiscale Modeling of Thin-Wire Coupling Problems Using Hybridization of Finite Element and Dipole Moment Methods and GPU Acceleration
ÖZGÜN, ÖZLEM; Mittra, Raj; Kuzuoğlu, Mustafa (2020-01-01)
In this article, a hybrid numerical method, called finite element method (FEM) + dipole moment (DM), is presented for efficient solution of multiscale electromagnetic radiation and scattering problems that involve structures with fine features, such as thin-wire antennas or objects. In this method, the FEM is hybridized with the DM approach to help ease certain computational burdens, such as mesh refinement, ill-conditioning, memory overload, and long computation times, when solving multiscale problems with...
Design and Optimization of Nanoantennas for Nano-Optical Applications
Işıklar, Göktuğ; Ergül, Özgür Salih; Department of Electrical and Electronics Engineering (2020-9)
In this study, design and simulation of plasmonic nanoantenna structures to obtain high power enhancement capabilities at optical frequencies, as well as utilization of nanoantennas for imaging and sensing applications are presented. Plasmonic characteristics of nanoantennas, which depend on many parameters, such as material, frequency, geometry, and size, are investigated in detail via computational analyses of various nanoantenna structures. Numerical solutions of electromagnetic problems are performe...
Citation Formats
H. İbili, “Computational simulation and realization of three-dimensional metamaterials with various exotic properties,” Thesis (M.S.) -- Graduate School of Natural and Applied Sciences. Electrical and Electronics Engineering., Middle East Technical University, 2019.