Kemal Delihacioglu

DESIGN OF POLARIZATION AND INCIDENT ANGLE INSENSITIVE DUAL-BAND METAMATERIAL ABSORBER BASED ON ISOTROPIC RESONATORS

Polarization and incident angle independent metamaterial-based absorber (MA) which acts as a strong dual-band resonator is designed and constructed. Besides, a method to design single/dual- band MA is presented in detail. The proposed model is based on isotropic ring resonator with gaps and octa-star strip (OSS) which allows maximization in the absorption because of the characteristic features of the structure. Re∞ection and absorption responses are obtained both numerically and experimentally and compared to each other. Two maxima in the absorption are experimentally obtained around 90% at 4:42GHz for the flrst band and 99:7% at 5:62GHz for the second band which are in good agreement with the numerical simulations (95:6% and 99:9%, respectively). The numerical studies verify that the dual-band MA can provide perfect absorption at wide angles of incidence for both transverse electric (TE) and transverse magnetic (TM) waves. The proposed model can easily be used in many potential application areas such as security systems, sensors, medical imaging technology.

TRANSMISSION TUNNELING THROUGH THE MULTILAYER DOUBLE-NEGATIVE AND DOUBLE-POSITIVE SLABS

Transmission tunneling properties and frequency response of multilayer structure are theoretically presented by using transfer matrix method. The structure is composed of double-negative and double-positive slabs which is sandwiched between two semi-inflnite free space regions. Double-negative layers are realized by using Lorenz and Drude medium parameters. The transmission characteristics of the proposed multilayer structure based on the constitutive parameters, dispersion, and loss are analyzed in detail. Finally, the computations of the transmittance for multilayer structure are presented in numerical results. It can be seen from the numerical results that the multilayer structure can be used to design e-cient fllters and sensors for several frequency regions.

Perfect metamaterial absorber-based energy harvesting and sensor applications in the industrial, scientific, and medical band

Abstract. An electromagnetic (EM) energy harvesting application based on metamaterials is introduced. This application is operating at the the industrial, scientific, and medical band (2.40 GHz), which is especially chosen because of its wide usage area. A square ring resonator (SRR) which has two gaps and two resistors across the gaps on it is used. Chip resistors are used to deliver the power to any active component that requires power. Transmission and reflection characteristics of the metamaterial absorber for energy harvesting application are theoretically investigated and 83.6% efficient energy harvesting application is realized. To prove that this study can be used for different sensor applications other than harvesting, a temperature sensor configuration is developed that can be applied to other sensing applications.

Transmission tunneling through the periodic sequence of double-negative and double-positive layers

Transmission tunneling based on the frequency behavior of a multilayer structure comprised of double-positive (DPG) and double-negative (DNG) layers is investigated. The structure is sandwiched between two identical half-spaces. The DNG layers are analyzed using Lorentz and Drude medium. Effects of the permittivity and permeability changes on the transmission are also examined for lossless and lossy situations. Finally, the transmission characteristics for the proposed multilayer structure are presented numerically. It can be seen that the multilayer structure may be used to design efficient filters for different frequency ranges.

Electromagnetic energy harvesting by using tunable metamaterial absorbers

In this study, electromagnetic (EM) energy harvesting by using metamaterial absorber is numerically explained. Operation frequency is 2.40 GHz since it is the industrial scientific and medical (ISM) band. This band is especially chosen due to most of the customer electronic devices are working in this band. Split ring resonator that have two splits on it used in this study, chip resistors are placed on these splits for wireless energy transfer to the devices. 83.6% efficient electromagnetic energy harvesting is theoretically realized.

Increasing bandwidth in antenna applications By using chiral metamaterials

Chiral metamaterials are such materials that cannot be found in the nature and show exotic properties as negative refraction index. One of the most important properties of chiral metamaterials is to show optical activity by changing the polarization of the electromagnetic wave. In this way, an electromagnetic wave can be directed and can be controlled. Furthermore, cross coupling is created between electric field and magnetic field in the chiral medium In this study, focusing gain and effects on the antenna applications are searched. Since chiral metamaterials have exotic properties, they have advantages in antennas, gain, bandwidth and designing small material dimensions. 1 GHz bandwidth is obtained in this study.

Chiral metamaterials with strong and dynamically optical activity

In this study, chiral metamaterial that creates strong optical activity and dynamical circular dichroism due to geometry of the structure (gammadion-bilayer cross-wires) is presented. It includes the gammadion with discontinuous bilayer cross wire patterned on opposite sides. The designed chiral metamaterial offers easier fabrication and more efficient result. Also, transmission and reflection coefficients, theta and chirality coefficient of the medium are independently analyzed. It provides strong and dynamical optical activity due to the high chirality. The experimental results match with the results of the numerical study.

Meanderline Based Microwave Polarization Rotator and Antireflector

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.