جستجوی مقالات مرتبط با کلیدواژه "metamaterial" در نشریات گروه "فیزیک"

We have investigated the optical properties of the double-periodic structure containing graphene-based hyperbolic metamaterial using the transfer matrix method and the effective medium theory at the Terahertz frequency region. Our findings reveal that this structure may have multiple band gaps in hyperbolic and elliptical frequency regions. Moreover, it shows that the transmission and absorption for TM polarization depend on both graphene chemical potential and optical axis orientation of the hyperbolic metamaterial layers. However, in the TE polarization case, these optical properties only depend on graphene chemical potential.

In this research, the electric, magnetic and structural behaviors of the Ag/Hf3NiOy nanostructures fabricated using the co-precipitation technique were studied. Since, the fabrication of ordered metallic structure arrays is habitually complex, the mass production of these structures is being prevented. In recent years, researchers have begun to explore materials with inherent DNG property. Metamaterials allow both field components of light to couple to meta-atoms and thus they enable entirely new optical properties and exciting applications.  Ag/Hf3NiOy disordered percolative composites contain conductive nanoparticles. When the concentration of metal nanoparticles in semi-continuous composites is less than the percolation threshold, the real part of the dielectric constant is positive. Also, the permeability constants can be controlled by silver content, meaning that this parameter is adjustable. Interestingly, decreased permeability was observed in samples with higher silver content. When the silver content exceeded the percolation threshold, silver networks were formed due to the interconnection of silver nanoparticles. The effective magnetic properties were due to the magnetic resonance and eddy current of the samples with an external magnetic field. The plasma oscillations of conduction electrons in the samples at a metallic state led to the negative permittivity.

In this paper, a novel dual-band bandpass filter for the measurement and optimization of Wi-Fi waves exposure in the non-ionizing frequency range of 2.4 and 5 gigahertz, has been designed and simulated. In the novel proposed method for detection, initially the Wi-Fi waves have been filtered and then converted to the direct current signal in the detector. This filter consists of a complementary split ring resonator metamaterial and an interdigital capacitor which has been printed on a 50 ohms coplanar waveguide with the Rogers 3003 dielectric. In the equivalent circuit model of the bandpass filter, the complementary split ring resonator has been represented by a tank circuit which is in parallel with the coplanar waveguide. The interdigital coupling capacitor is in series with the waveguide. By adjusting the complementary split ring resonator radius and the interdigital capacitor length, the frequency of transmission poles of the filter can be tuned. The electromagnetic coupling mechanism in the components has been discussed. According to the results of the scattering parameters curve, the return loss at the transmission poles is more than 40 dB while the insertion loss in passbands is less than 0.3 dB.

Due to the capability of tuning the electric conductivity of Graphene, this two dimensional material can be used in designing tunable metamaterials. In this article, two different metamaterials with unit cells in the form of slit ring resonators (SRR) and its complimentary (CSRR) are introduced and their effective electric permittivity modification with changing the chemical potential of graphene, dimension of the structure and incident light polarization is investigated. Comparing the effect of changing the dimension of the structure with chemical potential modification, shows that the first changes maximum of the effective permittivity in a more limited frequency range relative to the letter. Resonant frequency displacement of 16THz is achieved by changing the chemical potential of graphene from 0.3 to 0.45ev. Changing the polarization of the incident light will modify the charge and current distribution and the frequency range of maximum effective permittivity will be changed. Introduced structure in this article is an effective step in controlling the electromagnetic wave in the terahertz frequency range.