JOURNAL OF OPTOELECTRONICAL NANOSTRUCTURES
Year:2016 | Volume:1 | Issue:2|Papers Count:7

In this paper, we investigated the corrected plasmon dispersion relation for graphene in presence of a constant magnetic field which it includes a quantum term arising from the collective electron density wave interference effects. By using quantum hydrodynamic plasma model which incorporates the important quantum statistical pressure and electron diffraction force, the longitudinal plasmons are the electrostatic collective excitations of the solid electron gas. It shows the importance of quantum term from the collective electron density wave interference effects. By plotting the dispersion relation derived, it has been found that dispersion relation of surface modes depends significantly on Bohm’s potential and statistical terms and it should be taken into account in the case of magnetized or unmagnetized plasma; we have noticed successful description of the quantum hydrodynamic model. So, the quantum corrected hydrodynamic model can effectively describe the Plasmon dispersion spectrum in degenerate plasmas, since it takes into account the full picture of collective electron-wave interference via the quantum Bohm’s potential. By plotting the dispersion relation, the behavior of different wave types was predicted. It was found that one of them should not be propagated to the specific wave number. By drawing of contour curve of these modes, the areas that modes can be propagated were obtained.

The natural frequency and pull-in instability of clamped-clamped nano-actuators in the presence of a dielectric layer are analyzed. The influence of the presence of Casimir force, electrostatic force, fringing field effect, axial force, stretching effects and the size effect are taken into account. The governing equation of the dynamic response of the actuator is transformed in a non-dimensional form. The Galerkin decomposition method is employed to decompose the equations in time and space. Then, the obtained decomposed governing equations are solved numerically. The results show that the presence of the size effect and the axial force increases the natural frequency of the system. It is found that there is a unique value of the dielectric layer, in which the pull-in deflections of the nano-actuators are independent of the Casimir force, size effect and the axial loads. The advantage of this dielectric layer can be utilized in the design of nano-actuators and nano-sensors in the nanoscale.

Increasing development of nano-technology in optics and photonics by using modern methods of light control in waveguide devices and requiring miniaturization and electromagnetic devices such as antennas, transmission and storage as well as improvement in the electromagnetic tool, have led researchers to use the phenomenon of electromagnetically induced transparency (EIT) and similar phenomena in metamaterials. In this work, we introduce a metamaterial structure in nanometer dimensions and THz frequency region. Moreover, by broking the geometrical symmetry structure, we offer EIT with high transmittance and more Q-factor in comparison, to our knowledge, with previous studies of two-dimensional structure, in the infrared region. These achievements can be a good choice for slow light applications and can be used to amplify light in nanostructure and also to detect the infrared light. Finally, we study the effect of changing the metal on the proposed metamaterial. Moreover, in this study, numerical calculations and simulations are done by FDTD method.

In this paper a new optical channel drop filter (CDF) based on two dimensional (2-D) photonic crystals (PhC) with hexagonal shaped structure is proposed and numerically demonstrated by using the finite-difference-time-domain (FDTD) and plane-wave-expansion (PWE) techniques. Photonic crystals (PhCs) are artificial dielectric nanostructure materials in which a periodic modulation of the material dielectric constant results in a photonic band gap (PBG). By employing defects in the photonic crystals, light can steer in specific direction and consequently in the most of PhC applications, defects are used in their structures. The proposed structure is consisted of two series hexagonal shaped rings of Si rods between two straight waveguides to improve the performance of the channel drop filter. By analyzing the proposed structure, wide ranges of TE photonic band gap (PBG) would be achieved. It will be indicated that the proposed channel drop filter has appropriate characteristics and can be used in future WDM communication systems.

Cu (In, Ga) Se2 thin films (CIGS) on metallic substrate (titanium, molybdenum, aluminum, stainless steel) were prepared by a two-step selenization of Co-evaporated metallic precursors in Se-containing environment under N2 gas flow. Structural properties of prepared thin film were studied. To characterize the optical quality and intrinsic defect nature low-temperature photoluminescence, were performed. Results shows that the structural and optical properties of Cu (In, Ga) Se2 thin films strongly depend on the growth condition, charactristics of substrate and chemical composition. In2S3 thin layer has been used as buffer layer in CIGS solar cells and physical properties of them investigated. Solar cells were completed by vacuum deposition of ZnO/ZnO: Al layers and Ni/Al contact fingers. The surface morphology and bulk composition of thin films were investigated by scanning electron microscopy (SEM) equipped with energy-dispersive X-ray spectroscopy (EDS). The optical testing was carried out by recording transmittance spectra of the samples by spectrophotometers in the spectral range 190–3000 nm at a resolution of 1 nm. The better conversion efficiencies were around 12.0 %.

We describe how to obtain electronic transport properties of disordered graphene, including the tight binding model and nearest neighbor hopping. We present a new method for computing, electronic transport wave function and Greens function of the disordered Graphene. In this method, based on the small rectangular approximation, break up the potential barriers in to small parts. Then using the finite difference method, the Dirac equations of disordered graphene, reduce to the discrete matrix equation. The discrete matrix equation is solved by direct and Green’s function methods. In this method, geometry of disorder plays an important role. This method allows for an amenable inclusion of several disorder mechanisms at the microscopic level. The effect of impurity on the transmission probability and conductivity are obtained, using the electronic transport wave function. The results show that, for the conductance, geometry plays an important role. In addition, by transmission probability and using Landau formula, the Fano factor is investigated.

In this article, we suggested a novel design of polarization splitter based on coupler waveguide on InP substrate at 1.55mm wavelength. Photonic crystal structure is consisted of two dimensional (2D) air holes embedded in InP/InGaAsP material with an effective refractive index of 3.2634 which is arranged in a hexagonal lattice. The photonic band gap (PBG) of this structure is determined using the plane wave expansion (PWE) method by RSOFT Bandsolve software. Band diagram also show an overlap of two photonic bandgaps for both TE and TM about 1.55 mm wavelength. Also, the band structure is calculated for a lattice constant of 625 nm and a radius of 266.6 nm. The proposed polarization splitter has a transmission spectral of 75% and 70% for the TE and TM polarized light, respectively. The proposed polarization splitter is realized in a standard semiconductor technology on InP substrate at 1.55 m wavelength and can be easily monolithically integrated with other planar integrated circuits.