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Öğe Dynamical Chiral Metamaterial with Giant Optical Activity and Constant Chirality Over a Certain Frequency Band(Applied Computational Electromagnetics Soc, 2016) Karadag, F.; Comez, I.; Dincer, F.; Bakir, M.; Karaaslan, M.We demonstrate numerically and experimentally a dynamical chiral metamaterial that uniaxially creates giant optical activity and circular dichroism. In addition, the structure gives a high negative refractive index due to the large chirality. The proposed chiral metamaterial includes four L attached cross (FLAC) wire strips and offers a simple geometry, flexibility and more efficient results for chiral metamaterial applications such as polarization rotator, EM filter and so on. The experimental results are in a good agreement with the numerical simulation. It can be seen that FLAC wire strips based chiral metamaterial can also be used to achieve natural-small chirality with a constant value in a wide frequency range between 3.5-4.5 GHz. This is also another crucial feature of the structure. Therefore, the proposed chiral metamaterial with constant chirality value can be used to design novel EM devices such as polarization converter, anti-reflection filters for a certain frequency range.Öğe Photonic band gap engineering in two-dimensional photonic crystals and iso-frequency contours(Taylor & Francis Ltd, 2014) Erdiven, U.; Karadag, F.; Karaaslan, M.; Unal, E.; Dincer, F.; Sabah, C.We have theoretically investigated photonic band structures of two-dimensional (2D) photonic crystals (PCs) in air background. The lattices consist of the rotated and modified square dielectric rods. The influence of opto-geometric parameters of designed unit-cell structures are analyzed in terms of opening frequency gaps and appearing tilted band graphs by applying plane wave expansion method. Optimum structures with large photonic band gaps are notified. In order to get gap maps, the gaps as a function of the size and the rotation angle of the square rods are calculated. So, the band gaps of transverse magnetic and transverse electric polarization modes indicate symmetry in point of the rotation angle and these band gaps overlap. Thus, the smallest width of the narrow air veins is founded as 0.06a. The results show almost 40nm complete width of the air veins for mid-gap wavelength =1.55m. This result shows the fabrication capability of these optimized PC structures.Öğe Planar Photonic Crystals Biosensor Applications of TiO2(Polish Acad Sciences Inst Physics, 2012) Erdiven, U.; Karaaslan, M.; Unal, E.; Karadag, F.We examine quality factor and sensitivity change depending on the resonant wavelength changing refractive index of surrounding liquid for TiO2 photonic crystal slab structure. Photonic crystal slab structure is used widely for biological materials such as proteins, antigens, DNA, cells, virus particles and bacteria. Mentioned photonic crystal slabs are usable with large-area biosensor designs. They permit direct access to externally incident optical beams in a microfluidic device. Model calculations are based on two-dimensional periodic crystal structure. Photonic crystal slab consists of a square lattice of air holes in a finite-thickness dielectric slab. The time domain simulations were implemented by software MIT Electromagnetic Equation Propagation.Öğe Systematic Analysis on the Optical Properties of Chiral Metamaterial Slab for Microwave Polarization Control(Applied Computational Electromagnetics Soc, 2015) Comez, I.; Karaaslan, M.; Dincer, F.; Karadag, F.; Sabah, C.Theoretical and numerical of investigation of the chiral slab exhibiting polarization rotation is presented in detail. The effects of the chirality, thickness of medium, dielectric constant, and incident angle are analyzed in order to display the characteristic features of the chiral slab both for TE and TM incident waves. The chiral slab then is realized by using a full wave EM simulation software in order to validate the numerical results in which the numerical and simulation results are in good agreement with each other. Different than the other studies existing in literature, the proposed model shows optimum results for wide frequency band by using small chirality which is sufficient for polarization rotation. From the results, it is observed that the proposed system and its realization can be effectively used as a polarization converter and EM filters at some frequencies.
