Browsing by Subject "Split ring resonators"
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Item Open Access Development of left-handed composite materials and negative refracting photonic crystals with subwavelength focusing(SPIE, 2005) Özbay, EkmelWe review the studies conducted in our group concerning electromagnetic properties of metamaterials and photonic crystals with negative effective index of refraction. In particular, we demonstate the true left handed behavior of a 2D composite metamaterial, by analyzing the electric and magnetic response of the material components systematically. The negative refraction, subwavelength focusing, and flat lens phenomena using 2D dielectric photonic crystals are also presented.Item Open Access Electromagnetically induced left-handedness in a dense gas of three-level atoms(The American Physical Society, 2004) Oktel, M. Ö.; Müstecaphoǧlu, Ö. E.Ways in which a three-level system can be used to change the frequency-dependent magnetic permeability of an atomic gas were discussed. The resulting macroscopic electrodynamics was also discussed. The two levels were separated at optical frequencies while having a nonvanishing magnetic dipole matrix element. It was found that such level splittings require large external magnetic fields.Item Open Access EU NoE metamorphose: Metamaterials research activities(SPIE, 2005) Özbay, EkmelWe will present the activities of METAMORPHOSE a network of excellence (NoE) formed under EU-FP6 on the area of metamaterials. The main scientific objective of the partners of this consortium is to develop new types of artificial materials, referred to below as metamaterials, with electromagnetic properties that cannot be found among natural materials. The results of this development should lead to a conceptually new range of radio, microwave, and optical technologies, based on revolutionary new materials made by large-scale assembly of some basic elements (nanoscopic and microscopic) in unprecedented combinations. Further information on this NoE can be found in http://www.metamaterials-eu.org.Item Open Access Experimental demonstration of sub-wavelength imaging by left handed metamaterials(SPIE, 2007) Özbay, EkmelWe review the studies conducted in our group concerning electromagnetic properties of metamaterials and photonic crystals with negative effective index of refraction. In particular, we demonstate the true left handed behavior of a 2D composite metamaterial, by analyzing the electric and magnetic response of the material components systematically. The negative refraction, subwavelength focusing, and flat lens phenomena using left handed metamaterials and photonic crystals are also presented.Item Open Access Ferroelectric based tuneable SRR based metamaterial for microwave applications(IEEE, 2007) Özbay, Ekmel; Aydın, Koray; Bütün, Serkan; Kolodziejak, K.; Pawlak, D.We discuss the possibility of achieving tunable split ring resonators at microwave frequencies. One method is to use varying capacitance values to tune the magnetic resonance frequency. As another method ferroelectric thin films can be employed to obtain active response from the split ring resonators. We report the experimental measurements that are performed for single split ring resonators at microwave frequencies.Item Open Access Metamaterial inspired enhanced far-field transmission through a subwavelength nano-hole(WILEY, 2010-06-02) Alici, K. B.; Özbay, EkmelIn the present study, we first demonstrate the polarization and orientation dependent transmission response of split ring resonators at the infrared and visible band. Then, we numerically demonstrate a configuration for the enhancement of power passing through an electrically small hole. By using deep subwavelength optical split ring resonator antennas and couplers we achieved a 400-fold enhanced transmission from a subwavelength aperture area of the electrical size Λ 2/25. The power was transmitted to the far field with 3.9 dBi directivity at 300 THz. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) Transmission through a subwavelength aperture at the optical regime is quite low. The Letter by Alici and Ozbay shows how it can be enhanced and transferred to the far field by using a metamaterial inspired configuration composed of nano-scale split ring resonator antennas and couplers. A 400-fold power enhancement was achieved.Item Open Access Microwave resonators enhanced with 3D liquid-metal electrodes for microparticle sensing in microfluidic applications(Institute of Electrical and Electronics Engineers , 2023-11-22) Alataş, Yağmur Ceren; Tefek, Uzay; Sari, B.; Hanay, Mehmet SelimIn electrical sensing applications, achieving a uniform electric field at the sensing region is required to eliminate the compounding effect of particle location on the signal magnitude. To generate a uniform electric field in a microfluidic platform, 3D electrodes based on conductive electrolyte liquids have been developed before, where the ionic conductivity of the electrolyte was sufficient for impedance measurements at low frequencies (typically lower than 50 MHz). However, electrolyte liquids cannot be used as electrodes at microwave frequencies (>1 GHz) due to the low mobility of ions. Here, we used Galinstan, a room-temperature liquid metal, to microfabricate 3D liquid electrodes connected to a microwave resonator — and all integrated within a microfluidic system. By generating a highly uniform electric field, a mixture of 20 μm and 30 μm diameter polystyrene particles were measured and analyzed without any calibration for particle position. The results demonstrate the utility of liquid electrodes in enhancing the electrical characteristics of microwave resonant sensors.Item Open Access Miniaturization and characterization of metamaterial resonant particles(IEEE, 2008-10) Aznar, F.; Bonache, J.; Martín, F.; Özbay, Ekmel; Alıcı, K. Boratay; Bilotti, F.; Tricarico, S.; Vegni, L.; Baena, J. D.; Jelinek, L.; Marqués, R.This paper is focussed on the miniaturization and characterization of semi-lumped resonators, of interest for the synthesis of metamaterial-based structures such as metamaterial transmission lines, frequency selective surfaces, absorbers, and radiating elements, among others. The particles consist on metallic patterns etched on a dielectric and are inspired on the split ring resonator, SRR (that is, the formerly resonant particle used for the synthesis of left handed metamaterials). The different strategies for miniaturization are discussed and examples are given. It is shown that by using two metallic levels connected through vias it is possible to achieve very small electrical size for the particles (namely, below λ/100, where λ is the wavelength in the considered substrate at resonance). A method to determine the electrical parameters of the resonators in metamaterial transmission line configurations is also presented, and the possibility to determine the characteristics of the isolated particles is discussed. Finally, examples of application of this technique are presented. This work is of interest for the synthesis of effective media metamaterials based on resonant elements. © 2008 EuMA.Item Open Access Multi-gap individual and coupled split-ring resonator structures(Optical Society of American (OSA), 2008) Penciu, R.S.; Aydin, K.; Kafesaki, M.; Koschny Th.; Özbay, Ekmel; Economou, E.N.; Soukoulis, C.M.We present a systematic numerical study, validated by accompanied experimental data, of individual and coupled split ring resonators (SRRs) of a single rectangular ring with one, two and four gaps. We discuss the behavior of the magnetic resonance frequency, the magnetic field and the currents in the SRRs, as one goes from a single SRR to strongly interacting SRR pairs in the SRR plane. We show that coupling of the SRRs along the E direction results to shift of the magnetic resonance frequency to lower or higher values, depending on the capacitive or inductive nature of the coupling. Strong SRR coupling along propagation direction usually results to splitting of the single SRR resonance into two distinct resonances, associated with peculiar field and current distributions. © 2008 Optical Society of America.Item Open Access Observation of negative refraction and negative phase velocity in true left-handed metamaterials(SPIE, 2005) Özbay, EkmelWe report a true left-handed (LH) behavior in a composite metamaterial consisting of periodically arranged split ring resonator (SRR) and wire structures. The magnetic resonance of the SRR structure is demonstrated by comparing the transmission spectra of SRRs with that of closed SRRs. We confirmed experimentally that the effective plasma frequency of the LH material composed of SRRs and wires is lower than the plasma frequency of the wires. A well-defined left-handed transmission band with a peak value of -1.2 dB (-0.3 dB/cm) is obtained. We also report the transmission characteristics of a 2D composite metamaterial (CMM) structure in free space. At the frequencies where left-handed transmission takes place, we experimentally confirmed that the CMM structure has effective negative refractive index. Phase shift between consecutive numbers of layers of CMM is measured and phase velocity is shown to be negative at the relevant frequency range. Refractive index values obtained from the refraction experiments and the phase measurements are in good agreement. The experimental results agree extremely well with the theoretical calculations.Item Open Access Optimization and tunability of deep subwavelength resonators for metamaterial applications: complete enhanced transmission through a subwavelength aperture(Optical Society of American (OSA), 2009) Alici, K.B.; Bilotti F.; Vegni L.; Özbay, EkmelIn the present work, we studied particle candidates for metamaterial applications, especially in terms of their electrical size and resonance strength. The analyzed particles can be easily produced via planar fabrication techniques. The electrical size of multi-split ring resonators, spiral resonators, and multi-spiral resonators are reported as a function of the particle side length and substrate permittivity. The study is continued by demonstrating the scalability of the particles to higher frequencies and the proposition of the optimized particle for antenna, absorber, and superlens applications: a multi-spiral resonator with ë/30 electrical size operating at 0.810 GHz. We explain a method for tuning the resonance frequency of the multi-split structures. Finally, we demonstrate that by inserting deep subwavelength resonators into periodically arranged subwavelength apertures, complete transmission enhancement can be obtained at the magnetic resonance frequency. © 2009 Optical Society of America.Item Open Access Simulation and micro-fabrication of optically switchable split ring resonators(Elsevier BV, 2007-10) Gundogdu, T. F.; Gökkavas, M.; Güven, K.; Kafesaki, M.; Soukoulis, C. M.; Özbay, EkmelThe effect of conductivity variation as a proposed method for the investigation of photoconductive switching properties of split ring resonators (SRRs) is simulated. Three different systems that are applicable under certain fabrication and/or optical excitation conditions are described. The simulated transmission spectrum indicates that for a large range of dark conductivity values, complete switching of the SRR resonance is possible. One of the simulated systems, involving split ring resonators on Si substrate, was fabricated and characterized. The transmission spectrum of that system was measured, with the Si in its high-resistivity state, and a 60 dB dip between 108 and 115 GHz, due to SRRs magnetic resonance, was observed