Browsing by Subject "Composite metamaterials"

Now showing 1 - 7 of 7

Open Access
Experimental observation of cavity formation in composite metamaterials
(Optical Society of American (OSA), 2008) Caglayan H.; Bulu I.; Loncar, M.; Özbay, Ekmel
In this paper, we investigated one of the promising applications of left-handed metamaterials: composite metamaterial based cavities. Four different cavity structures operating in the microwave regime were constructed, and we observed cavity modes on the transmission spectrum with different quality factors. The effective permittivity and permeability of the CMM structure and cavity structure were calculated by use of a retrieval procedure. Subsequently, in taking full advantage of the effective medium theory, we modeled CMM based cavities as one dimensional Fabry-Perot resonators with a subwavelength cavity at the center. We calculated the transmission from the Fabry-Perot resonator model using the one-dimensional transfer matrix method, which is in good agreement with the measured result. Finally, we investigated the Fabry-Perot resonance phase condition for a CMM based cavity, in which the condition was satisfied at the cavity frequency. Therefore, our results show that it is possible to treat metamaterial based cavities as one-dimensional Fabry-Perot resonators with a subwavelength cavity. © 2008 Optical Society of America.
Open Access
Experimental observation of true left-handed metamaterial
(IEEE, 2005) Aydın, Koray; Güven, Kaan; Özbay, Ekmel
We report a true left-handed (LH) behavior in composite metamaterials. The magnetic resonance of the SRR structure is demonstrated. Plasma frequency of the LH material is shown to be lower than that of the wires.
Open Access
The magical world of metamaterials
(IEEE, 2009-10) Özbay, Ekmel
In recent years, there has been a burgeoning interest in rapidly growing field of metamaterials due to their unprecedented properties unattainable from ordinary materials. Veselago pointed out that a material exhibiting negative values of dielectric permittivity (ε) and magnetic permeability (μ) would have a negative refractive index [1]. Generally speaking, the dielectric permittivity (ε) and the magnetic permeability (μ) are both positive for natural materials. In fact it is possible to obtain negative values for ε and μ by utilizing proper designs of metamaterials. Left-handed electromagnetism and negative refraction are achievable with artificially structured metamaterials exhibiting negative values of permittivity and permeability simultaneously at a certain frequency region. The first steps to realize these novel type of materials were taken by Smith et al., where they were able to observe a left-handed propagation band at frequencies where both dielectric permittivity and magnetic permeability of the composite metamaterial are negative [2]. Soon after, left-handed metamaterials with an effective negative index of refraction are successfully demonstrated by various groups [3].
Open Access
Negative refraction and subwavelength focusing using left-handed composite metamaterials
(SPIE, 2008-01) Özbay, Ekmel; Aydın, Koray
We review experimental studies performed on left-handed metamaterials (LHM) at microwave frequencies. The metamaterial structure is composed of periodic arrays of split-ring resonators and wire meshes and exhibits a left-handed propagation band at frequencies of negative permittivity and negative permeability. Negative refraction is verified using prism shaped LHM and also by beam-shifting method. Subwavelength focusing of a point source is achieved with a resolution of 0.13λ, through a flat LHM superlens.
Open Access
Observation of defect formation in metamaterials
(OSA, 2008-10) Çağlayan, Hümeyra; Bulu, I.; Loncar, M.; Özbay, Ekmel
We report subwavelength localization of electromagnetic fields within cavities based on metamaterials. Cavity resonances are observed in the transmission spectrum of a split ring resonator and composite metamaterials cavity structures. These cavity resonances are shown to exhibit high quality factors. Since the unit cells of metamaterials are much smaller than the operation wavelength, subwavelength localization is possible within these metamaterial cavity structures. In the present paper, we show that the electromagnetic field is localized into a region of λ/8, where λ is the cavity resonance wavelength.
Open Access
Retrieval of effective parameters for bianisotropic metamaterials with omega shaped metallic inclusions
(Elsevier, 2011-11-18) Li, Z.; Aydin, K.; Özbay, Ekmel
Bianisotropic metamaterials including Ω-shaped metallic elements are investigated experimentally and theoretically. A passband is observed for a composite metamaterial (CMM) based on an Ω-medium below the plasmonic frequency of the corresponding closed CMM. The effective parameters (refractive index, impedances, permittivity, permeability, and magnetoelectric coupling coefficient) are retrieved for the Ω-medium and the CMM based on it. Our retrieval results show that the passband observed for the CMM is a band with positive refractive indices. Our retrieval results confirm the deductions of our previous reports.
Open Access
Transmission properties of composite metamaterials in free space
(American Institute of Physics, 2002) Bayındır, Mehmet; Aydin, K.; Özbay, Ekmel; Markoš, P.; Soukoulis, C. M.
We propose and demonstrate a type of composite metamaterial which is constructed by combining thin copper wires and split ring resonators (SRRs) on the same board. The transmission measurements performed in free space exhibit a passband within the stop bands of SRRs and thin wire structures. The experimental results are in good agreement with the predictions of the transfer matrix method simulations. © 2002 American Institute of Physics.