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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 Electromagnetic absorbance properties of a textile material coated using filtered arc-physical vapor deposition method(Sage Publications Inc, 2015) Esen, M.; Ilhan, I.; Karaaslan, M.; Unal, E.; Dincer, F.; Sabah, C.We explore the structure of a textile absorber in terms of its electromagnetic and absorption properties in the microwave region. Its absorption characteristics are similar to those reported for various metamaterial-based absorbers, exhibiting absorption as high as 98% at resonance. In addition, the angular behavior of the absorption properties of the sample reveal incident angle independency, which is the other added value of the study. Also, the suggested textile absorber has a simple configuration, which introduces flexibility to adjust its material properties and easily tune its structure to suit other frequencies. The proposed textile absorber and its variations have myriad potential applications in radar technology, long distance radio telecommunication, and so on. Although in its current state the proposed structure provides almost perfect absorption covering a wide range of microwave C-Band, the developing technology will soon allow manufacturing textiles that can manipulate lights, leading to the design of invisibility cloak and other science fiction devices besides finding important application areas in medical science.Öğe Meanderline based microwave polarization rotator and antireflector(2012) Karaaslan, M.; Ünal, E.; Delihacio?lu, K.; Bhadauria, A.; Tetik, E.We showed analytically that a chiral slab can exhibit both optical activity and antireflection. Oblique incident waves depending on permittivity, chirality and thickness of bulk chiral material are investigated. The analytical calculations are numerically achieved by meander line metamaterial. © 2012 IEEE.Öğe Microstrip Patch Antenna Covered With Left Handed Metamaterial(Applied Computational Electromagnetics Soc, 2013) Dogan, E.; Unal, E.; Kapusuz, D.; Karaaslan, M.; Sabah, C.We present gain characteristics of microstrip patch antennas covered with metamaterial substrate composed of split-ring resonators (SRRs) and metallic strip. To determine the performance of the SRR-metallic strip mounted on microstrip patch antenna, the metamaterial has been proposed as an effective medium with extracted constitutive parameters. Simulation results are supported by experimental measurements. The experimental results confirm that the metamaterial covered patch antenna improves gain by an amount of -5.68 dB (% 60.3) as well as radiation pattern (-8 dB to +20 dB) at WLAN communication.Öğe Multi-band metamaterial absorber: Design, experiment and physical interpretation(Applied Computational Electromagnetics Society (ACES), 2014) Dincer, F.; Karaaslan, M.; Unal, E.; Akgol, O.; Sabah, C.This paper presents the design, fabrication, characterization and experimental verification of a perfect Multi-Band Metamaterial (MTM) absorber (MA) based on a simple configuration of a rectangular resonator and strips operating in microwave frequency regime. The proposed multi-band MA provides perfect absorption with TE-incident angle independency. Maximum absorption rate is achieved as 99.43% at 5.19 GHz for simulation and 98.67% at 5.19 GHz for experiment, respectively. The measurement results of the fabricated prototype are in a good agreement with the numerical results. Furthermore, we introduce a numerical analysis in order to show physical interpretation of the MA mechanism in detail. Additionally, a sensor application of the proposed multi-band MA is presented to demonstrate an extra feature of the suggested structure. As a result, the proposed multi-band MA enables myriad potential application areas such as radar, stealth, shielding, communication, imaging and medical applications. © 2014 ACES.Öğe Multi-Band Metamaterial Absorber: Design, Experiment and Physical Interpretation(Applied Computational Electromagnetics Soc, 2014) Dincer, F.; Karaaslan, M.; Unal, E.; Akgol, O.; Sabah, C.This paper presents the design, fabrication, characterization and experimental verification of a perfect Multi-Band Metamaterial (MTM) absorber (MA) based on a simple configuration of a rectangular resonator and strips operating in microwave frequency regime. The proposed multi-band MA provides perfect absorption with TE-incident angle independency. Maximum absorption rate is achieved as 99.43% at 5.19 GHz for simulation and 98.67% at 5.19 GHz for experiment, respectively. The measurement results of the fabricated prototype are in a good agreement with the numerical results. Furthermore, we introduce a numerical analysis in order to show physical interpretation of the MA mechanism in detail. Additionally, a sensor application of the proposed multi-band MA is presented to demonstrate an extra feature of the suggested structure. As a result, the proposed multi-band MA enables myriad potential application areas such as radar, stealth, shielding, communication, imaging and medical applications.Öğe New-Generation Chiral Metamaterials Based on Rectangular Split Ring Resonators With Small and Constant Chirality Over a Certain Frequency Band(Ieee-Inst Electrical Electronics Engineers Inc, 2014) Sabah, C.; Dincer, F.; Karaaslan, M.; Akgol, O.; Demirel, E.; Unal, E.Chiral metamaterials (MTMs), a new class of MTMs, provide a simpler solution for obtaining negative refraction and dynamic electromagnetic response. Many research groups have been studying chiral MTMs asking for strong chiral behaviors such as optical activity and circular dichroism. These studies have generally focused on the properties of a large chirality and circular dichroism. However, small and constant chirality over a certain frequency band have not been queried so far in the literature. In fact, this area is mostly ignored by the researchers. This study numerically and experimentally focuses on small and constant chirality with a new-generation planar chiral MTM based on rectangular split ring resonators (SRRs), in details by using two different geometries. We have successfully obtained small chirality values by using the proposed designs, which can be easily integrated into many interesting applications such as transmission and antireflection filters or polarization control devices.Öğe Optimization of elliptically designed patch mushrooms and investigation of low profile dipole antenna - HIGP interaction(Natl Inst Optoelectronics, 2010) Unal, E.; Karaaslan, M.; Ozdemir, E.In this study, we investigate high impedance ground plane structures consist of elliptic metallic mushrooms. In this structure gaps and metallic patch dimensions have an effect on electromagnetic band gap is observed. It is shown that elliptic mushrooms can show much better performance compared to its conventional counterpart such as perfectly electric conductor. Good return loss in the EBG frequency range for HIGP-low profile dipole antenna is obtained. Miniaturized and improved antenna system is satisfied by this new elliptic mushrooms.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 Polarization Angle Independent Metamaterial Absorber in both of C- and X-Bands(Applied Computational Electromagnetics Soc, 2015) Karaaslan, M.; Demirci, A. O.In this study, perfect metamaterial absorbers (MAs) based on circle- and square-shaped configurations that are numerically and experimentally designed and analyzed in both of C- and X-band. The proposed models have very simple designs and present perfect absorption for all polarization angles. A sensor application of the suggested model (for circle-shaped) is also presented to introduce further feature of the structure. Moreover, the suggested models can be easily reconfigured for THz and infrared frequency regimes to enable myriad potential applications such as sensors, defense systems and stealth in the next studies.Öğe Polarization angle independent metamaterial absorber in both of C- and X-bands(Applied Computational Electromagnetics Society (ACES), 2015) Karaaslan, M.; Demirci, A.O.In this study, perfect metamaterial absorbers (MAs) based on circle- and squareshaped configurations that are numerically and experimentally designed and analyzed in both of C- and X-band. The proposed models have very simple designs and present perfect absorption for all polarization angles. A sensor application of the suggested model (for circle-shaped) is also presented to introduce further feature of the structure. Moreover, the suggested models can be easily reconfigured for THz and infrared frequency regimes to enable myriad potential applications such as sensors, defense systems and stealth in the next studies. © 2015 ACES.Öğe Polarization Angle Independent Perfect Metamaterial Absorber(Ieee, 2014) Dincer, F.; Karaaslan, M.; Unal, E.; Akgol, O.; Demirel, E.; Sabah, C.This paper presents a perfect metamaterial absorber (MA) based on rings and cross wires (RCWs) configuration in microwave frequency regime. Maxima absorption rate is 99.9 % at 2.76 Ghz for simulation and 99.4% at 2.82 GHz for experiment, in order. The proposed MA provides perfect absorption with angle of polarization independency. Consequently, suggested model enable myriad potential applications such as stealth and military technologies.Öğe Polarization angle independent perfect metamaterial absorber(Institute of Electrical and Electronics Engineers Inc., 2014) Dincer, F.; Karaaslan, M.; Unal, E.; Akgol, O.; Demirel, E.; Sabah, C.This paper presents a perfect metamaterial absorber (MA) based on rings and cross wires (RCWs) configuration in microwave frequency regime. Maxima absorption rate is at for simulation and at for experiment, in order. The proposed MA provides perfect absorption with angle of polarization independency. Consequently, suggested model enable myriad potential applications such as stealth and military technologies. © 2014 IEEE.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.Öğe Tunable perfect metamaterial absorber and sensor applications(Springer, 2016) Bakir, M.; Karaaslan, M.; Dincer, F.; Delihacioglu, K.; Sabah, C.Operation frequencies of traditional metamaterial absorbers are fixed meaning that it is not possible to change that frequency after the fabrication. Therefore, more studies are focused on the design of Tunable metamaterial absorber (TMA) since it is important to expand operation frequency. If the impedance of one or more layers of an absorber can be changed according to the applied electrical optical signal, then it would be possible to realize tunable absorbing designs. However, TMA studies reported previously are mainly focused on absorbing mechanism at microwave frequencies. In this study, TMA with varactor diode is designed and analyzed for absorber and sensor configurations. TMA is constructed by using a simple rectangular-shape geometry having two splits and a varactor diode placed at the right split. Numerical and experimental results show that perfect absorption is achieved when 0-10 V reverse bias voltage is applied. Resonance frequency can be easily tuned by changing the reverse bias voltage. Frequency dependent absorption behavior of TMA is presented with respect to different incident angles for TE and TM polarizations. A sensor application, knowing the absorption resonance frequency can provide the ability to determine the temperature of materials. The novelty of the study is to determine the temperature or the other parameters such as humidity or pressure by using TMA. It is also possible to determine the material type or its density if limited resource such as frequency generator is present.
