Advanced Research Laboratories (ARL)

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Browsing Advanced Research Laboratories (ARL) by Author "Alıcı, Kamil Boratay"

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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.