Hamzeh M. Jaradat

Design and Simulation of Fully Printable Conformal Antennas with BST/Polymer Composite Based Phase Shifters

A fully printable and conformal antenna array on a flexible substrate with a new Left- Handed Transmission Line (LHTL) phase shifter based on a tunable Barium Strontium Titanate (BST)/polymer composite is proposed and computationally studied for radiation pattern correction and beam steering applications. First, the subject 1 × 4 rectangular patch antenna array is configured as a curved conformal antenna, with both convex and concave bending profiles, and the effects of bending on the performance are analyzed. The maximum gain of the simulated array is reduced from the flat case level by 34.4% and 34.5% for convex and concave bending, respectively. A phase compensation technique utilizing the LHTL phase shifters with a coplanar design is used to improve the degraded radiation patterns of the conformal antennas. Simulations indicate that the gain of the bent antenna array can be improved by 63.8% and 68% for convex and concave bending, respectively. For the beam steering application, the proposed phase shifters with a microstrip design are used to steer the radiation beam of the antenna array, in planar configuration, to both negative and positive scan angles, thus realizing a phased array antenna.

Infrared (IR) Absorber Based on Multiresonant Structure

In this letter, an absorber design is introduced that has a very wide absorption band at normal incidence over the midrange infrared (IR) wavelength regime. The proposed structure is comprises four layers, where the extra layer adds a degree of freedom in optimizing the response compared the conventional three-layered absorbers (dielectric spacer sandwiched between a ground thin film and a resonant conducting pattern). The simulations revealed a broadband absorption region that extends from 3 up to 12 μm of light wavelength achieving more than 120% of full bandwidth at half-maximum (FWHM).

Experimental Demonstration of Negative Index of Refraction in Magnetic Semiconductors

Homogeneous negative index materials have been introduced as an alternative to conventional metamaterials designs. Based on direct experimental evidence, we demonstrate that the magnetic semiconductor, Cr-doped indium oxide, possesses a negative refractive index near 28.0 μm. This effect is based on the coexistence of the magnon mode with the plasmonic mode, with simultaneous negative permeability and permittivity responses. Thin films of In2-xCrxO3 are fabricated, and the magnetic measurements clearly demonstrate ferromagnetism with a high saturation magnetization and a Curie temperature which is much higher than room temperature. The refractive index is extracted from combined transmittance and reflectance data and is compared with the theoretical prediction. Moreover, a direct experimental method is used to demonstrate negative refraction in this material.

Numerical Simulation of Gold Nanostructure Absorption Efficiency for Fiber-Optic Photoacoustic Generation

In many non-destructive testing and medical diagnostic applications, photoacoustic generation by optical flber is an efiective approach to meet the requirements of broad bandwidth and compact size. The energy absorption layer coated onto the flber endface plays an important role in the conversion of laser energy into heat used to excite acoustic waves. Gold nanostructures are promising solutions to be utilized as energy absorption layers due to their capability of absorbing maximum optical energy at plasmon resonant frequencies. The appropriate selection of the organization and dimensions of the gold nanostructures is the key to achieving high absorption e-ciency. Numerical modeling is an e-cient way to predict the behavior of the system as a variation of select parameters. A 3D flnite integral technique model was established to simulate the dependency of absorption e-ciency on the organization and dimensions of the gold nanospheres and nanorods. The simulation results provided practical clues to the design and fabrication of flber-optic photoacoustic generators.

Negative refractive index in ferromagnetic semiconductors: experimental verification

In this work, we show that natural crystals, or magnetic semiconductor, Cr-doped indium oxide, has a negative refractive index at ~ 27.8 micron wavelength. The effect was predicted by two of us a few years ago (A.G. Kussow and A. Akyurtlu, Phys. Rev. B, 78, 205202 (2008)). Our result seriously undermines wide-spread opinion that only composite artificial metamaterials can demonstrate negative refractive index. Thin ferromagnetic films of ICO were fabricated by original post-annealing sputtering method. FTIR R and T measurements were processed to extract refractive index within the range of interest. The extracted from combined transmittance and reflectance FTIR data negative refractive index band parameters are found to be close to expected one.

Experimental demonstration of negative index of refraction in magnetic semiconductors

Homogeneous negative refractive index materials are introduced as an alternative to normally utilized inhomogeneous metamaterials. The theory of such materials was developed several years ago (A. Kussow and A. Akyurtlu, PRB 78, 205202 (2008)), and the effect is due to the coexistence of the spin-wave mode with the plasmonic mode, and both modes are activated by the electromagnetic field with simultaneous negative permittivity and permeability responses within the narrow frequency band close to the ferromagnetic resonance. To justify this theory, the thin films of ferromagnetic semiconductor, Cr-doped indium oxide, were fabricated, with clearly measured ferromagnetism at high saturation magnetization and a Curie temperature which is much higher than room temperature. The refractive index, within mid-IR, was extracted from combined transmittance and reflectance data and was compared with theoretical prediction. Also, a direct standard beam displacement method validates the effect of negative refraction in this material.

Broadband Infrared (IR) metamaterial absorber

In this work a Metamaterial (MTM) absorber design is introduced that has a very wide absorption characteristics over the midrange Infrared (IR) band, the proposed structure comprised of 4 layers, the extra layer adds a degree of freedom in optimizing the response compared the conventional 3-layered absorbers. The simulations revealed a broadband absorption region that extends from 3μm up to 12μm of light wavelength.

A Novel Mathematical Model to Realizing Randomness in Full-Wave Simulations of Regularly Arranged Nanoparticles

In this letter, a mathematical correction factor is introduced to realize randomly distributed spherical nanoparticles embedded in a dielectric. A full-wave electromagnetic analysis is used to model the unit cell structure so as to simulate the Lewin formulation for uniformly distributed particles. The proposed correction factor is needed to predict the randomly distributed particles, eliminating the necessity of simulating large number of particles, which has a significant impact on the structure complexity, computer memory resources, and simulation time.