Browsing by Subject "Split-ring resonator"

Now showing 1 - 9 of 9

Open Access
Accurate modeling of metamaterials with MLFMA
(ESA Publications, 2006) Ergül, Özgür; Ünal, Alper; Gürel, Levent
Electromagnetic modelling of large metamaterial (MM) structures employing multilevel fast multipole algorithm (MLFMA) is reported. MMs are usually constructed by periodically embedding unit cells, such as split-ring resonators (SRRs), into a host medium. Without utilizing any homogenization techniques, we accurately model large numbers of unit cells that translate into very large computational problems. By considering all of the electromagnetic interactions, the resulting dense matrix equations are solved iteratively with the accelerated matrix-vector products by MLFMA. To increase the efficiency, we also employ parallel computing in the solutions of large SRR problems.
Open Access
Bilayer metamaterial: analysis of left-handed transmission and retrieval of effective medium parameters
(Institute of Physics Publishing Ltd., 2007) Guven, K.; Cakmak, A. O.; Caliskan, M. D.; Gundogdu, T. F.; Kafesaki, M.; Soukoulis, C. M.; Özbay, Ekmel
We report an experimental and numerical analysis of a planar metamaterial designed for normal-to-plane propagation, and operating at microwave frequencies. The metamaterial consists of cutwire and wire patterns, which are arranged periodically on both sides of a dielectric layer, in the form of a bilayer. The left-handed transmission band of the metamaterial is demonstrated experimentally. The effective index of refraction retrieved from the S parameters is found to be negative within this transmission band. An independent negative refraction experiment supports the existence of the negative index of refraction for the metamaterial.
Open Access
Computational analysis of complicated metamaterial structures using MLFMA and nested preconditioners
(IEEE, 2007-11) Ergül, Özgür; Malas, Tahir; Yavuz, Ç; Ünal, Alper; Gürel, Levent
We consider accurate solution of scattering problems involving complicated metamaterial (MM) structures consisting of thin wires and split-ring resonators. The scattering problems are formulated by the electric-field integral equation (EFIE) discretized with the Rao-Wilton- Glisson basis functions defined on planar triangles. The resulting dense matrix equations are solved iteratively, where the matrix-vector multiplications that are required by the iterative solvers are accelerated with the multilevel fast multipole algorithm (MLFMA). Since EFIE usually produces matrix equations that are ill-conditioned and difficult to solve iteratively, we employ nested preconditioners to achieve rapid convergence of the iterative solutions. To further accelerate the simulations, we parallelize our algorithm and perform the solutions on a cluster of personal computers. This way, we are able to solve problems of MMs involving thousands of unit cells.
Open Access
Continuously tunable terahertz metamaterial employing magnetically actuated cantilevers
(Optical Society of American (OSA), 2011) Ozbey, B.; Aktas O.
Terahertz metamaterial structures that employ flexing microelectromechanical cantilevers for tuning the resonance frequency of an electric split-ring resonator are presented. The tuning cantilevers are coated with a magnetic thin-film and are actuated by an external magnetic field. The use of cantilevers enables continuous tuning of the resonance frequency over a large frequency range. The use of an externally applied magnetic field for actuation simplifies the metamaterial structure and its use for sensor or filter applications. A structure for minimizing the actuating field is derived. The dependence of the tunable bandwidth on frequency is discussed. © 2011 Optical Society of America.
Open Access
Fast and accurate analysis of large metamaterial structures using the multilevel fast multipole algorithm
(2009) Gürel, Levent; Ergül, Özgür; Ünal, A.; Malas, T.
We report fast and accurate simulations of metamaterial structures constructed with large numbers of unit cells containing split-ring resonators and thin wires. Scattering problems involving various metamaterial walls are formulated rigorously using the electric-field integral equation, discretized with the Rao-Wilton-Glisson basis functions. Resulting dense matrix equations are solved iteratively, where the matrix-vector multiplications are performed efficiently with the multilevel fast multipole algorithm. For rapid solutions at resonance frequencies, convergence of the iterations is accelerated by using robust preconditioning techniques, such as the sparse-approximate-inverse preconditioner. Without resorting to homogenization approximations and periodicity assumptions, we are able to obtain accurate solutions of realistic metamaterial problems discretized with millions of unknowns.
Open Access
Labyrinth based left-handed metamaterials and sub-wavelength focusing of electromagnetic waves
(SPIE, 2006) Özbay, Ekmel; Bulu, İrfan; Çağlayan, Hümeyra
We propose and demonstrate a resonant structure that solves two major problems related to the split-ring resonator structure. These major problems may be stated as the bianisotropy and electric coupling to the magnetic resonance. These two problems introduce difficulties in obtaining isotropic left-handed metamaterial mediums. The resonant structure that we propose here solves both of these problems. We further show that in addition to the magnetic resonance, when combined with a suitable wire medium, the structure that we propose exhibits left-handed transmission band. We further demonstrate the sub-wavelength focusing of electromagnetic waves by use of a two dimensional labyrinth based metamaterial. Our experimental results showed that it is possible to focus the source field with half widths as small as λ/4 by using the labyrinth based metamaterial.
Open Access
Metamaterials with negative permeability and negative refractive index: Experiments and simulations
(Institute of Physics Publishing Ltd., 2007) Özbay, Ekmel; Guven, K.; Aydin, K.
We report the transmission characteristics of split-ring resonator and left-handed metamaterials (LHM) in the microwave frequency regime. A left-handed transmission band is observed at the frequencies where both dielectric permittivity and magnetic permeability are negative. The reflection characteristics of ordered and disordered LHMs are studied. The two-dimensional LHM structure is verified to have a negative refractive index. We employed three different methods to observe negative refraction: the beam shift method, refraction through wedge-shaped negative-index metamaterial, and phase-shift experiments.
Open Access
Microfluidics for reconfigurable electromagnetic metamaterials
(AIP Publishing, 2009) Kasirga, T. S.; Ertas, Y. N.; Bayındır, Mehmet
We propose microfluidics as a useful platform for reconfigurable electromagnetic metamaterials. Microfluidic split-ring resonators (MF-SRRs) are fabricated inside a flexible elastomeric material by employing rapid prototyping. The transmission measurements performed for mercury-injected MF-SRR exhibits sharp magnetic resonances at microwave wavelengths. We further calculate transmission properties of the MF-SRR array and the effect of electrical conductivity of the liquid inside the channel on the magnetic resonance. The measured results agree well with numerical calculations. Our proposal may open up directions toward switchable metamaterials and reconfigurable devices such as filters, switches, and resonators.
Open Access
Transmission properties of various split-ring resonator systems
(Optical Society of America, 2006) Aydın, Koray; Bulu I.; Güven, K.; Özbay, Ekmel
We investigated the magnetic resonance of split-ring resonators (SRR) experimentally. The dependence of the geometrical parameters on the resonance frequency of SRR is studied. We further investigated the effect of disorder on performance of SRRs. © 2006 Optical Society of America.