Scholarly Publications - ARL

Permanent URI for this collectionhttps://hdl.handle.net/11693/115569

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Browsing Scholarly Publications - ARL by Author "Aydın, Koray"

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    Experimental analysis of true left-handed behaviour and transmission properties of composite metamaterials
    (Elsevier, 2005-12) Güven, Kaan; Aydın, Koray; Özbay, Ekmel
    We report the true left-handed transmission of a composite metamaterial (CMM) consisting of periodically stacked split-ring resonator (SRR) and wire elements. The negative permeability (μ < 0) gap is demonstrated explicitly by comparing SRR and closed-ring resonator structures. We confirm experimentally that the plasma cut-off frequency of the CMM is determined by the combined dielectric response of SRR and wire elements, and it is much lower than that of the wire-only medium. This is crucial to identify the left-handed transmission bands of the CMM. We further investigate the effect of intralayer and interlayer disorder on the transmission spectrum of CMM arising from misaligned fabrication and stacking of the SRR layers. We found that the intralayer disorder affects the μ < 0 gap of SRRs and the left-handed transmission band of CMM significantly, whereas the SRR transmission is rather immune to interlayer disorder.
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    Negative refraction and subwavelength focusing using photonic crystals
    (SPIE, 2005-01) Özbay, Ekmel; Aydın, Koray; Alıcı, Kamil Boratay; Güven, Kaan
    We review certain novel optical properties of two-dimensional dielectric photonic crystals (PCs) which exhibit negative refraction behavior. We investigate two mechanisms which utilize the band structure of the PC and lead to a negative effective index of refraction (neff < 0). The negative refraction phenomenon is demonstrated experimentally and by simulations when the incident beam couples to a photonic band with neff < 0. Further, the PC slab acts like a focusing lens to an omnidirectional source where the properties of focusing depends on the details of the band structure. In one case, by utilizing the TM polarized first band, an image of the source can be formed in the vicinity of the interface with subwavelength resolution. In another case, a TE polarized upper band is used which is able to focus the omnidirectional field far away from the interface with a resolution on par with the wavelength. In the latter case, we explicitly show the flat lens behavior of the structure. These examples indicate that PC based lenses can surpass limitations of conventional lenses and greatly enhance and extend optics applications.
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    Spectral negative refraction and focusing analysis of a two-dimensional left-handed photonic crystal lens
    (American Physical Society, 2004-11) Güven, Kaan; Aydın, Koray; Alıcı, Kamil Boratay; Soukoulis, C. M.; Özbay, Ekmel
    We report the spectral refraction analysis and focusing properties of a two-dimensional, dielectric photonic crystal (PC) slab in freespace. A transverse electric polarized upper band of the crystal is used. The measured refraction spectra indicates that a highly isotropic negative index of refraction is present in the measured frequency range of the band. We demonstrate experimentally and numerically the focusing of the field emitted from an omnidirectional source placed in front of the crystal. Both the source and the focus pattern are away from the PC interfaces of the order of several wavelengths. The focus pattern mimics the arbitrary lateral and longitudinal shifts of the source, which is a manifestation of true flat lens behavior.