Browsing by Author "Economou, E. N."
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Item Open Access Compact planar far-field superlens based on anisotropic left-handed metamaterials(American Physical Society, 2009-09-15) Shen, N.-H.; Foteinopoulou, S.; Kafesaki, M.; Koschny, T.; Özbay, Ekmel; Economou, E. N.; Soukoulis, C. M.Pendry’s perfect lens has spurred intense interest for its practical realization at visible frequencies. However, fabrication of low-loss isotropic left-handed metamaterials is a current challenge. In this work, we theoretically show that under specific conditions anisotropic metamaterial slabs can emulate Pendry’s perfect-lens phenomenon on a plane. Geometric optics leads to a new lens formula for this special anisotropic metamaterial superlens, which allows significant shrinkage of the metamaterial slab thickness for a certain range of far-field operation. Conversely, such anisotropic metamaterial superlens with the same thickness as its isotropic analog can operate for much larger distances between object and lens. We present numerical simulations which confirm our theoretical calculations. In particular, we find subdiffraction focusing that rivals the perfect isotropic negative-index metamaterial lens performance and obeys the new lens formula as predicted. In addition, we demonstrate that it is possible to attain far-field superfocusing with a metamaterial slab as thin as half the free-space wavelength. We believe this work will inspire new anisotropic metamaterial designs and opens a promising route for the realization of compact far-field superlenses in the visible regime.Item Open Access Left-and right-handed transmission peaks near the magnetic resonance frequency in composite metamaterials(American Physical Society, 2004) Katsarakis, N.; Koschny, T.; Kafesaki, M.; Economou, E. N.; Özbay, Ekmel; Soukoulis, C. M.We present free-space microwave measurements on composite metamaterials (CMMs) consisting of split ring resonators (SRRs) and wires either on the same dielectric board or on alternating boards. Our experimental results disprove the widely held belief that the occurrence of a CMM transmission peak within the stop bands of the SRRs alone and wires alone constitutes a clear demonstration of left-handed (LH) behavior. This belief is based on the assumption that the stop bands of SRRs alone and wires alone are not affected by the simultaneous presence of both. We show here that this assumption is wrong: The effective plasma frequency, ω′p, of the CMM is actually substantially lower than the wires-only plasma frequency, ωp; furthermore, the in-plane wires, as opposed to the off-plane case, push the magnetic resonance frequency of the SRRs, ωm, to a higher value, ω′m, for the CMM. We conclude that the criterion for deciding whether a peak in the transmission spectrum through a CMM is really left-handed is for the peak to be located above ω′m and below ω′p. Our results provide a definite way for experimentally identifying ω′p.