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In this article, we determine the elevated temperature of hot carriers in Graphene layer (Tel) in a waveguidefed Graphene FET (GFET) and examine its effect on photo-thermoelectric current that can be sensed at the electrodes of the GFET. Also we introduce an improvement in the Tel and, accordingly, photo-thermoelectric current by adding a second waveguide at the top of the device to produce a coupled...
A half power divider using ridge gap waveguide technology is realized in millimeter wave frequencies. By machining a piece of metal the divider was fabricated. There is no need to an electrical connection between the divider constitutive parts. The fabricated divider is self-packaged. Cylindrical pins are used in the divider structure for ease of fabrication. Low loss power division and good isolation...
The ultrathin graphene metasurface is proposed and analyzed as a cloaking shell for cylindrical objects with the aim of wideband tunable scattering cancellation in terahertz (THz) spectrum. This mantle cloak is structured by periodic array of graphene nanopatches. In this paper, it is analytically shown that the metasurface reactance can be tuned from inductive to capacitive, as a function of the...
A novel structure for THz photoconductive antennas (PCA) has been proposed to enhance the optical absorption, and consequently the power conversion efficiency. In the proposed structure, the surface of the low-temperature-grown GaAs (LTG-GaAs) substrate is textured to create an array of nanodisks where an array of silver nanodisks is placed 300 nm under the surface. The simulation results indicate...
Terahertz spectroscopy is a useful and an efficient method for detection of pure materials and also mixture compounds. In the present study the terahertz spectra of the α-lactose, high explosives RDX and also the binary mixture of mentioned materials has been obtained in the transition mode. The obtained spectra of the pure materials were in a very good agreement with literatures in the range of 0...
In this paper, five different nanoantenna structures, i.e. dipole, bowtie, rounded bowtie, rounded cross bowtie and cross bowtie nanoantennas are investigated for solar energy harvesting. Electrical field enhancement by each structure is investigated when different metals (silver, aluminum, gold, and copper) are used to achieve the best performance for solar energy harvesting. Field enhancement in...
Based on Photo-thermoelectric effect, by illuminating the active area of graphene-based optoelectronic devices, strong electron-electron interactions of the photo-excited carriers along with inherit inefficiency of electron-lattice energy relaxation in graphene, results in a sustained population of hot carriers. Furthermore, according to this effect, using generated hot-carrier temperature profile...
This paper presents the first-ever millimeter wave on-chip antenna (AoC) in 28 nm CMOS technology. The addition of artificial magnetic conductor (AMC) can increase the antenna's power gain and radiation efficiency to −1.75 dBi and 22%, respectively, with an occupied area of 0.95 mm×4.75 mm at 38 GHz. This structure is intended for fully integrated single-chip nanometer CMOS transceivers for 5G communication...
In this work, a graphene based plasmonic absorber with two absorption peaks of 0.99 and a wide full width at half maximum (FWHM) between the wavelengths of 1455 and 1610 nm is presented. The proposed absorber is composed of a single layer of graphene that covers the nanostructure with an array of ring and L-shaped grooves on a metal film. The light absorption is more due to the localized surface plasmons...
In this paper, an absorber with two nested split ring resonators (SRRs) is introduced that its absorption spectrum has three absorption peaks by the values of 99.8%, 97.52%, and 94.98% at the frequencies of 8.5, 14.7 and 23.9 THz, respectively. In order to understand the performance of the absorber, the proposed structure is excited in two different situations. The simulation results reveal that when...
A multiple-input-multiple-output (MIMO) dual-band antenna system consisting of two elements, each of which built up of circularly polarized slotted patch antenna for mm-wave band 5G wireless handheld and portable terminals is described. Space diversity is used to achieve a good independent channel fading in MIMO systems. In theoretical analysis of MIMO systems often assume that each antenna is isolated...
In this paper, a pulsed THz imaging system in normal geometry is presented experimentally and the effect of placing a pinhole in front of a covered sample on image quality has been investigated too. Also, the improvement of image quality by using ray transfer matrix is described theoretically. Finally, by using contour system the results are evaluated and the accuracy of THz imaging system is tested.
Using metamaterial structures, a novel Infrared (IR) detector is proposed to operate at the frequency of 180 THz. It has been shown that using metamaterials can concentrate the field in the semiconductor region (here InGaAsSb) resulting in higher absorption and higher detectivity for the IR detector. The proposed structure has been analyzed using full wave numerical methods. The simulation results...
We propose a new vertical graphene plasmonic directional coupler as a terahertz cross-bar switch. The directional coupler is constructed of two pattern-free graphene plasmonic waveguides. The lateral confinement of surface plasmon polaritons is accomplished based on the similar mechanism used in dielectric loaded waveguides. An ultrashort switching length of 360 nm is obtained at the frequency of...
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