JOURNAL OF OPTOELECTRONICAL NANOSTRUCTURES
Year:2017 | Volume:2 | Issue:3|Papers Count:7

First principle calculations of nano layered ZnO polymorphs (Wurzite–, Zinc blende–, Rocksalt–structures) in the scheme of density functional theory were performed with the help of full potential linear augmented plane wave (FP-LAPW) method. The exchange - correlation potential is described by generalized gradient approximation as proposed by Perdew–Burke–Ernzrhof (GGA–PBE) and modified Becke–Johnson (mBJ) approximation. The electronic behavior and the optical properties of the structures are investigated and compared to experimental data, where available. The electronic structure of w–ZnO and z–ZnO revealed a 3.01 eV and 2.59 eV direct energy gap in (G®G) direction by applying mBJ potential. In contrast to w– and z–ZnO the electronic structure of r–ZnO shows an indirect 2.81 eV energy gap in (G®G) direction. Reflectivity, transmittance and refractive index spectra for three nano layered of ZnO phases in Uv – visible region have been calculated. The electron effective mass values at the bottom of conduction band were evaluated for the three geometries.

In this paper, the localized TM surface waves of a nonlinear self-focusing left-handed slab sandwiched between a uniform medium and a one-dimensional photonic crystal (1D PC) is analytically investigated. Our method is based on the first integral of the nonlinear Maxwell's equations. For the TM surface waves, the presence of two electric field components makes the analysis difficult. Therefore, we used the uniaxial approximation for the nonlinear slab. The considered 1D PC can be a left-handed PC (made of alternate left-handed (LH) and right-handed material) or a usual PC. In these structures, we find that the nonlinear LHM slab allows to control the dispersion properties of p-polarized surface waves. It is shown that there are no surface modes in the linear regime in the conventional PC and by increasing the intensity of electromagnetic field to higher value, the surface modes are emerged. To confirm our achievements, we also compared the results obtained by this method and the attenuated total reflection (ATR) method.

Cobalt (Co) doped Zinc Oxide (ZnO) thin films, containing different amount of Cobalt nanoparticles as the Co doping source, deposited by the sol–gel spin coating method onto glass via annealing temperature at 400˚C, have been investigated by optical characterization method. The effect of Co incorporation on the surface morphology was clearly observed from scanning electron microscopy (SEM) images. Optical conductivity and optical constants such as absorption coefficient, reflectivity, extinction coefficient, and refractive index as a function of photon energy were calculated, and it was found that the doping with Co led to decrease absorption coefficient, extinction coefficient, refractive index and bandgap energy, while the optical conductivity increased at higher photon energies. The optical band gap depends on the Co doping level and on the particle size and crystallinity of the films and is in the range of 3.05– 3.17 eV. The optical band gap widening is proportional to the one-third power of the carrier concentration.

In this paper, an optical filter based on a two dimensional photonic crystal ring resonator (PCRR) with triangular lattice is designed and presented. For this purpose, the effects of positioning, arrangement and the number of the inner rods of the dual-curved PCRR on the performance characteristics of our optical filter such as the transmission coefficient and the quality factor have been fully investigated. Calculation results show that a transmission coefficient of 100% with a quality factor of 2400 at the operating wavelength of nearly 1576 nm can be achieved. The proposed optical filter comparatively performs better than the previously reported ones. In addition, this structure can be used for the design of optical multi-channel de multiplexer. To study the photonic band gap of our structure, the plane wave expansion (PWE) method has been used and the finite-difference time-domain (FDTD) method has also been employed to analyze the optical behavior of the proposed device.

Recently, photonic crystals doped with liquid crystal (LC) material have gained much research interest. In this article new ternary one-dimensional photonic crystal introduced and studied. The liquid crystal layer of 5CB and 5PCH is sandwiched by two dielectric layers. For the first time, we use four structures SiO2/UCF35/CaF2, SiO2/5CB/CaF2, NFK51/UCF35/NPSK53 and NFK51/5CB/NPSK53. The effect of temperature on transfer band gap of these photonic crystals is investigated with transferred matrix method. The results show that in all four structures PBG for extraordinary ray (ne) is very large than ordinary ray (no) and with increasing of temperature, PBG shifts to red wavelength. PBG width is very vast and variation of the figure with respect temperature is very sharp for SiO2/UCF35/CaF2 structure. Also, the suggested design takes high tunability due to the infiltration of the LC material. One can use the proposed structure as temperature sensing device, narrow band optical filter and in many optical systems.

In this paper we are going to calculate the correlation function and Bell's inequality for three qubit W state under the Lorentz transformations. This survey is based on the introduction of two different expressions of spin observable were presented by Lee-Young and Kim-Son.

In this paper, the properties of the defect mode in the photonic band gap of one-dimensional ternary photonic crystals containing high temperature superconductor layer (SPCs) have been theoretically investigated. We considered the quasi-periodic layered structures by choosing two order of ternary Thue-Morse structures with mirror symmetry. We investigated the transmission spectra of these structures by using the transfer matrix method and two-fluid model. It is found that the location of defect mode and the range of photonic band gap can be changed by the incident angle. So that, the defect mode blue-shifted and disappeared by increasing the incidence angle. We observed an omnidirectional photonic band gap for the TE polarization that its range is from 456nm to 520nm. Also, the defect mode can be tuned by the temperature. As a result, the width of defect mode can be decreased by increasing the temperature, especially in the vicinity of the critical temperature of superconductor layer. This kind of SPCs has potential applications in filters, sensors and so on.