Çeşitli sıradışı özelliklere sahip üç boyutlu metamalzemelerin hesaplamalı benzetimleri ve gerçeklenmeleri.

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.Thesis (M.S.) -- Graduate School of Natural and Applied Sciences. Electrical and Electronics Engineering

Very Low-Cost Inkjet-Printed Metamaterials: Progress and Challenges

A very low-cost inkjet printing of three-dimensional metamaterials is studied. By using commercial standard printers and loading them with silver-based inks, we are able to fabricate metamaterial blocks that can operate effectively at the lower frequencies of the X-band. We discuss important challenges in constructing a low-cost inkjet printing setup, as well as the current status on fabricating successful structures without resorting to expensive setups. Despite the challenges, it is shown that relatively complex metamaterial blocks that operate at microwave frequencies can be fabricated

Design and Fabrication of Low-Cost Inkjet-Printed Metamaterials

We consider three-dimensional metamaterials involving split-ring resonators (SRRs) that are produced by using low-cost inkjet printing. Following their three-dimensional computational simulations, sensitivity analysis is applied on SRR arrays in order to evaluate their tolerance to various fabrication errors. We use silver-based inks in standard commercial printers in order to fabricate SRRs and their arrays. Measurements demonstrate the feasibility of fabricating very low-cost three-dimensional metamaterials using simple inkjet printing

Homogenization of Microwave Metamaterial Structures Using Full-Wave Solutions and Genetic Algorithms

Metamaterials involve small details that create challenges in their numerical analysis. As commonly practiced, homogenization of such complex structures may simplify and facilitate their numerical solutions. However, homogenization should be performed carefully to avoid excessive modeling errors, especially for finite structures. In this paper, we present accurate homogenization of three-dimensional metamaterials involving split-ring resonators (SRRs). Electromagnetic characteristics of finite SRR structures are found by rigorous optimization via genetic algorithms, while necessary numerical simulations are accurately performed by using the multilevel fast multipole algorithm. The results demonstrate the promising effectiveness of the approach for realistic metamaterial structures

MFIE-Based Formulation Using Double-Layer Modeling for Perfectly Conducting Objects

We present resonance-free solutions of scattering problems involving closed conductors using the magnetic field integral equation (MFIE). In the literature, MFIE is often combined with the electric-field integral equation (EFIE) to avoid internal resonances that can significantly contaminate solutions especially when scatterers become electrically large. The resulting combined-field integral equation (CFIE), however, possesses the disadvantages of EFIE, e.g., ill-conditioning for dense discretizations. We show that placing an interacting inner surface inside the given object and enforcing internal fields to be zero can mitigate internal resonances, making MFIE resonance free without employing EFIE. Using an arbitrary inner surface can significantly suppress internal fields; but, as also shown in this contribution, the size of the inner surface, i.e., the distance between inner and outer surfaces, can be critical to obtain accurate results that are comparable to those obtained with the conventional CFIE

Mitigating internal resonances of the magnetic-field integral equation via double-layer modeling

We present a new method to mitigate internal resonances of the magnetic-field integral equation (MFIE) for closed conductors, without combining this equation with the electric-field integral equation (EFIE) that is commonly practiced in the literature. For a given object and its surface, a smaller closed surface is placed inside to create a double layer. This way, the magnetic field intensity is enforced to zero on the inner surface, making the overall solution unique at all frequencies. By eliminating the need for EFIE, the resulting implementation is purely based on MFIE interactions. In addition to its formulation, the initial numerical results of the proposed method on canonical problems are presented. © 2018 Institution of Engineering and Technology

Demonstration of negative refractive index with low-cost inkjet-printed microwave metamaterials

We present low-cost fabrications of inkjet-printed metamaterials that are resonating at microwave frequencies. A very low-cost setup involving commercial desktop printers loaded with silver-based inks is constructed and used to fabricate the metamaterials. We show that, despite the challenges in the low-cost fabrication processes, successful prints, and metamaterial samples can be obtained. A composite metamaterial design, which possesses a bandlimited transparency due to the induced negative refractive index, is fabricated and tested to demonstrate the feasibility of low-cost metamaterials with relatively complex geometries involving three-dimensional arrangements

Inkjet-printed frequency-selective structures based on improvedarrangements of U-shaped resonators

We present design, simulation, and fabrication of thin inkjet-printed frequency-selective structures involving U-shaped resonators. In order to obtain both multiband and polarization-independent operation, resonators are carefully arranged to construct thin structures. The designed arrangements are fabricated in a very low-cost inkjet-printing setup that is based on conventional printers loaded with silver-based inks. Initial results demonstrate favorable properties of the designs and their prototypes, demonstrating the feasibility of low-cost, but effective, frequency-selective structures