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Öğe Conformal Talbot-effect-focusing performance of nested gallium-doped zinc oxide nanorings at communication wavelength(Elsevier, 2020) Aslan, EkinMetasurfaces, artificial microand nano-photonic structures can modify wavefront of electromagnetic waves to the desired form. Metalenses are the metasurfaces assuming the role of focusing light. The focusing performance of nested gallium-doped zinc oxide nanoring-arrangements functionalized by conformal Talbot effect is inves-tigated for communication wavelength 1550 nm. The Talbot-effect-focusing performance of the 2D finite-sized structures are computationally demonstrated in a systematically manner. The impact of geometrical parameters on the primary focal spot and focusing performance parameters such as numerical aperture, full-width half maximum, focal depth, efficiency, and fill-factor is examined and summarized via finite difference time-domain numerical simulations. All samples presenting an alternative plasmonic option in this work yield a good focusing efficiency of >50%, absolute efficiency of >19%, numerical aperture up to 0.67, focal depth up to 1.4 times of focal length, and a wide focal spot size up to 6.0654 times of operating wavelength. As a result of finite-sized construction, conformal Talbot effect is examined from a novel alternative plasmonics perspective. Thus, a new planarized focusing platform is employed by using a nanostructured microlens, acting conformal transformation optics devices with low-cost and light capturing tolerance.Öğe An effective triple-band enhanced-infrared-absorption detection by honeycomb-shaped metamaterial-plasmonic absorber(Elsevier Science Sa, 2019) Aslan, Erdem; Aslan, Ekin; Saracoglu, Omer Galip; Turkmen, MustafaNowadays, accessing to new electromagnetic properties can be realized by fabricating metamaterials consist of artificial functional and subwavelength-scaled structures. Promoting artificial and functional metamaterial designs with large electromagnetic near-field enhancement especially over throughout multiband spectral range can provide critical contributions for infrared spectroscopy applications. In this context, the design and experimental realization of a photonic metamaterial are presented which can be utilized as an infrared biosensor. We utilize a honeycomb-shaped plasmonic nanoantenna for the design of the proposed novel absorber metamaterial. The fabrication and optical characterization of the structures are carried out and the sensor potential of the metamaterial is demonstrated through the detection of a polymer nanofilm. (C) 2019 Elsevier B.V. All rights reserved.Öğe Engineering the boosting of the magnetic Purcell factor with a composite structure based on nanodisk and ring resonators(Taylor & Francis Ltd, 2022) Aslan, Erdem; Aslan, EkinThe dependence of the optical communication interconnects on the electronics technology is a limitation for ultra-high-speed communications. Nanophotonics promises intriguing technologies to exceed these limitations. In this context, a silicon-based composite nanostructure is proposed to boost the magnetic Purcell enhancement one order of magnitude higher than a single hollow-disk resonator. The boosting effect relies on the near-field interaction between a hollow disk resonator and two larger rings. The engineering of the device is presented via simulations with the aim of obtaining the highest Purcell enhancement. Additionally, to reveal the underlying mechanism, the contribution of each multipole mode to the scattered intensity and near-field enhancement properties are analysed. Finally, the dependence of the Purcell factor on the position of the source is investigated. The results of this study may have a great potential to realize nanoscale light sources to be used in all-photonic chips for ultra-high-speed optical networks.Öğe Graphene-tunable mid-infrared metamaterials based on titanium nitride nanorods(Süleyman Demirel Üniversitesi, 2020) Aslan, Erdem; Aslan, EkinGraphene-tunable, particle-based and absorber metamaterials are presented whichutilize titanium nitride as the plasmonic material. The design of the particle-basednanoantenna array is shown via geometrical parameter sweep simulations.Additionally, the origin of the resonance mode is revealed by decomposing thespectrum into the radiating contributions of multipoles and near-fieldenhancement distribution maps. Moreover, the tunability of the designedmetamaterial is shown by changing the chemical potential of a monolayer ofgraphene which is coated on top of the device. To utilize the designed device as anabsorber metamaterial, a mirror layer is introduced for the elimination of thetransmission through the device. With the aim of obtaining perfect absorption, thethickness values of the functional layers are optimized via parameter sweepsimulations. Finally, the tunability of the absorber metamaterial is shown byutilizing a graphene monolayer on top of the nanoantennas and the tuningperformance of both architectures are compared. The engineering of graphenetunable metal-free metamaterials provides a novel strategy for the development oflow-cost integrated photonic devices and plasmonic devices which are resistant tohigh temperatures.Öğe Lensing for optical communication by diffraction from Peano curve-based fractal with alternative plasmonic material(Elsevier Gmbh, 2021) Aslan, EkinFocusing performance of Peano space filling curve-based fractal construction is studied at communication wavelength of 1550 nm. Lensing by diffraction from these finite-sized 2D devices of the first three iterated fractal lattice system constructed with gallium-doped zinc oxide is computationally demonstrated in a systematical manner. In this regard, focusing performance parameters such as efficiency, spot size, focal length, focal depth, and fill-factor are determined on the basis of geometrical parameter sweep and fractal generation through finite difference timedomain simulations. Focusing efficiency from 48% up to 60%, absolute efficiency from 14% up to 33.98%, numerical aperture values from 0.127 up to 0.96, spot sizes from 1.02 lambda SP up to 11.25 lambda SP, and focal depth larger than focal length are introduced by all computational samples. A conformal Talbot effect is assigned when appropriate geometric values are provided. A novel perspective is offered by a newly adapted fractal lattice to optics via an alternative plasmonic material perspective, especially for an optical fiber component.Öğe A microlens by gallium doped zinc oxide-nanoantenna(Süleyman Demirel Üniversites, 2020) Aslan, Ekin; Aslan, ErdemAlternative plasmonics based fractal microlens are investigated. In this context, lensing performance of gallium-doped zinc oxide Sierpinski carpet-based fractal construction functionalized by conformal Talbot effect is analyzed for communication wavelength 1550 nm. Focusing via diffraction from these 2D finitesized and two-iterated fractal lattice system is computationally demonstrated. In this regard, focusing performance parameters are computationally examined on the basis of geometrical parameter sweep and fractal generation via finite difference time-domain numerical simulations. Focusing efficiency > 50%, absolute efficiency > 18%, and focal depth larger than primary spot size are introduced by all computational samples. Moreover, a conformal Talbot effect is exhibited by this novel alternative plasmonics construction. A novel perspective based on alternative plasmonics by a newly adapted fractal design to optics is proposed. Thus, this fractal microlens is presented as a new planarized focusing platform, acting a conformal transformation optics device for light capturing tolerance and low-cost.Öğe Sinüzoidal kırışık duvarlı yarı-sonsuz paralel plakalı dalga kılavuzundan TEM modunda elektromanyetik dalgaların ışınımı(Hatay Mustafa Kemal Üniversitesi, 2011) Aslan, Ekin; Hameş, YakupDüzlemsel elektromanyetik dalgaların, dalga kılavuzundan ışınımı problemlerinin çözümünde, kılavuzun fiziksel ve geometrik yapısı önemli rol oynar. Genellikle tek başına Wiener-Hopf tekniği kullanılarak çözülebilen bu tip problemlerde, dalga kılavuzunun duvarlarında sinüzoidal kırışıklık olması durumunda ortaya çıkan çekirdek fonksiyonunun çözümü için sınır koşullarına pertürbasyon seri açılımları uygulanarak Wiener-Hopf eşitlikleri elde edilmesi ile çözülebilmektedir. Bu çalışmada, mükemmel iletken, yarı-sonsuz, paralel plakalı, sinüzoidal kırışıklıklı ve içi dielektrikle dolu bir dalga kılavuzundan TEM modunda düzlemsel dalganın ışınımı incelenmektedir. Geometrinin içerdiği sinüzoidal kırışıklıktan gelen karmaşıklıklar pertürbasyon metodu kullanılarak çözülmektedir.
