Çakmak, Atilla Özgür2016-01-082016-01-0820122012http://hdl.handle.net/11693/15700Cataloged from PDF version of article.Includes bibliographical references.The field of Electromagnetics encompasses several research areas and finds itself applications in all frequency ranges starting from very low frequencies up to optical wavelengths. Periodic structures offer a vast research area in Electromagnetics. Amongst these periodic configurations metamaterials and photonic crystals have been investigated in this study. Metamaterials (MTMs) are artificial materials which are carefully engineered to give outstanding electromagnetic responses, e.g. negative phase velocity, negative refraction. On the other hand, Photonic Crystals (PhCs) offer band stopping and full reflection at certain wavelengths and they are highly favored due their particular properties. PhCs are even commercially available nowadays in optical communication. In the first part of the study, we have been concentrated on the enhanced transmission through subwavelength apertures with the incorporation of the MTMs. Resonators that are inspired from the MTM research field are placed in the vicinity of the subwavelength apertures such that a near-field electromagnetic wave localization at the output side can be observed. The considered subwavelength apertures have poor transmission figures on the order of 1/10,000 (in terms of intensity) on the average throughout the investigated frequency band, which dramatically limits the propagation. We show that once the subwavelength resonators are allowed to interact with such subwavelength pertures, astonishingly high transmission enhancement figures (typically ranging from 30 dB up to 50 dB) can be attained, which in turn results in electromagnetic wave localization in the near-field. On top of these single aperture related studies, we investigated the propagation of the electromagnetic waves in aperture arrays. We explicitly distinguish the working mechanisms of the presently studied aperture arrays which also cause a transmission enhancement below the cutoff frequency of the regarding apertures. The transmission enhancement has been shown to be accompanied by the left handed propagation, which is a characteristic of the MTMs. We show that both right and left handed transmission channels can be opened simultaneously in these periodically stacked aperture arrays. Alternatively, we have worked on the graded-index PhCs (GRIN PhCs) in order to tailor the course of the propagating electromagnetic waves. It has been demonstrated that modified Gauss-Hermite modes are available in GRIN PhCs similar to the those in conventional homogenous GRIN structures that are already in use in the field of optics. The underlying physics of the propagation has been discussed and a focusing lens has been proposed, which is based on the GRIN PhCs. The proposed lens has been shown to provide improved input and output coupling figures for the waveguide configurations. The input coupling efficiency has been boosted by a factor of 8 dB, while the GRIN PhC at the output side of the waveguide achieved a collimated beam with 7 degrees of half power beam width according to the results of the far-field measurements. Lastly, PhC based gratings have been utilized to search for an optical diode. It has been shown that such a PhC grating can offer an extremely good contrast (on the order of 1000) between the intensities of the electromagnetic waves that are approaching from different sides of the proposed design. The working mechanism of the optical diode has been shown to rely on the gratings that opened higher order diffraction channels as the zeroth order diffractions are suppressed.xlii, 320 leaves ; illustrations ; 30 cm.Englishinfo:eu-repo/semantics/openAccessPhotonic crystalsMetamaterialsSubwavelength apertureThesisB133825