نشریه اپتوالکترونیک
سال سوم شماره 1 (پیاپی 8، پاییز و زمستان 1399)

In this paper, the temporal evolution of the nonlinear coherent states in a parametric oscillator in the presence of a Kerr medium is investigated. For this purpose, the Hamiltonian of the system is written in the interaction picture and as a combination of time-independent operators with time - dependent coefficients using an approximation method. Then, the temporal evolution of a nonlinear coherent state is obtained by exerting the corresponding time-evolution operator. In addition, the Mandel parameter, the auto - correlation function and the Husimi-Q distribution function of the time-dependent nonlinear coherent states in the parametric oscillator in a Kerr Medium are studied and analyzed.

Considering the reflection theory and numerous applications of the mirror, we can achieve mirrors with thin-film, metal-dielectric coatings. Hence, in this article, with respect to the above-mentioned approach and using new materials, a mirror with maximum reflection of nearly 100% and of aluminum alloy is produced. Metal mirror is a very good reflector with a wavelength of 3 to 5 micrometers. The optimum intermediate layer for inspecting metals' steam is aluminum oxide. This compound has higher stabilization compared to other intermediate layer substances. After optimizing the accumulation conditions and calculating the number and thickness of layers and the interface, the resulting collection was designed. The physical vapor method (pvd) and the thickness of layers are measured by optical method. By conducting qualitative tests and examining reflection spectrum, the durability and stability of the set have been investigated. The mirror aluminum has more than 99% reflection in infrared field.

A photonic crystal waveguide is provided in this article. The structure is two-dimensional array of silicon bars arranged in a triangular arrangement. Rods is placed in the air background and the x-z surface.  The waveguide structure is created by removing the silicon bars. In this splitter, band gap arrangement was investigated by FDTD method. The waveguide can play the role of a splitter. With this array, a two-port and three-port splitter has been created. The two-dimensional Splitter leads the waves in two channels. The three-port splitter permits electromagnetic waves to be emitted with a 180 ° phase shifted between output signals. In this three-port splitter, the measured transmission spectra shown that the guided mode can be separated into three different lights. Since the splitter is made up of the photonic crystal structure, it has fewer losses. This issue is an important matter in the photonic circuitry.

The Second Harmonic Generation has many applications. Since it is of particular importance, the current study examines its power and energy and irradiance conversion efficiencies for collimated Gaussian beams in presence of pump depletion and phase matching by using numerical calculations. In this paper, the optimal mode for the SHG (the Second Harmonic Generation) conversion efficiencies has been investigated in presence of pump depletion and phase matching, and it has been shown that the SHG conversion efficiencies in presence of pump depletion and phase matching depend only on the normalized incident peak irradiance. Therefore, the type of material used in the SHG can be selected properly according to the obtained results.

One of our current goals is the investigation of the fuel efficiency of DT by choosing a low Tritium fuel triac percentage, , in the new achievements of ICF, through the concept of quick combustion engines. This calculation certainly determines the possibility of using a quick combustion, and in particular the possibility of an appropriate stimulator, and explains the pulse duplex in the compressed material as well. In fact, in this research, our main goal is the study of the rate of gain changes with the change in the tritium concentration fraction. The lower the tritium concentration, the more economical it would be, but this amount should not be so low that affect the appropriate gain for fusion.

In this paper, the electrical properties of graphene and boron nitride are studied. The effect of the layers on each other and also the twisting of the layers on each other were studied. The presence of an additional layer creates additional levels, which, in the case of graphene, maintains the conductivity of the material, but reduces its mobility dramatically. The curvature of graphene and boron nitride increases the number of energy strips to eight. Increasing the bending angle leads to the movement of the point of attachment of the conduction edges and also to the movement of the capacity of the graphene to the center of the region of the brillouin. . In the case of boron nitride, the curvature transfers the band gap to the center of the brillouin region. This transmission increases with increasing the angles of twisting.

In this paper, temperature dependence of the magnetic susceptibility of the Mn12 magnetic molecular cluster is investigated in different fields. Until now, only dipole excitations were considered in calculations to calculate magnetic susceptibility, but due to the spin number of this molecular cluster and in order to obtain higher computational accuracy, more multipolar excitations should be included in the calculations. For this purpose, in this paper, in the calculations related to the magnetic susceptibility of the molecule, in addition to dipolar excitations, quadrupole excitations are also considered, and the relevant diagrams are drawn. Calculations show that the results obtained in a situation where quadrupole excitations are considered, are more consistent with the experimental results.

In this paper, functionalized carbon nanotubes were covered with a biocompatible shell of silica (MWCNT/SiO2). Having a high amount of OH groups, silica shells avoid nanotubes agglomeration and are able to uniformly capture and stabilize arbitrary amounts of nanoparticles on their surface. MWCNT/SiO2 doped with different amounts of Fe3O4 nanoparticles. Three samples of Fe3O4/SiO2/MWCNT nanocomposites prepared by 1, 2, and 3 weight ratio of Fe3O4 to SiO2/MWCNT are labeled S1, S2, and S3, respectively. Then, they were characterized by X-ray diffraction spectroscopy (XRD) and scanning electron microscopy (SEM). The magnetic property of samples was investigated with vibrational sample magnetometer (VSM), which indicated the superparamagnetic property of nanocomposites. Due to their biocompatibility, nanocomposites were used as recyclable photocatalysts to remove methylene blue dye.

In this paper, based on the perturbation theory, the energy eigenvalues of two, three, and four-layer quantum anti-dots are obtained. Using numerical calculations, the effects of the magnetic field, radius, and the number of layers of these nanostructures are investigated on 1S and 2P energy levels. The results of this study show that increasing the magnetic field, radius and the number of layers of quantum anti-dot increase the 1S and 2P energy levels. Further calculations show that the applied magnetic field sometimes causes new degeneracies, which can be seen in the 2P energy sublevels.

In this paper, the effect of a magnetic field on 2p energy levels of 〖Ga〗_(1-x) 〖Al〗_x As/GaAs/〖Ga〗_(1-x) 〖Al〗_x As quantum anti-dot has been investigated. To this aim, based on the perturbation theory and in the presence of an external magnetic field, the energy eigenvalue of the 2p state of this nano-structure is obtained. Then, on the basis of theoretical predictions and numerical calculations, it will be shown that the magnetic field does not always eliminate the degeneracies of energy levels and under certain conditions, the magnetic field itself is the cause of a new degeneracy in the energy levels. Furthermore, it is proved that changes in the height of the potential barrier will remove the degeneracy created after the application of the magnetic field.

By designing periodic structures of photonic crystals, electromagnetic waves can be reflected in a certain frequency range from their surface. Using the above feature, the emission of photons can be guided in the designed waveguide within the structure of photon crystal networks. One of the most important applications of photonic crystals is in the construction of logic gates. Therefore, in this paper, using the simulation method based on the numerical method of finite difference in time domain, the propagation of electromagnetic waves inside two-dimensional engineered photonic crystals is investigated and the structure of band gap and distribution of electric and magnetic fields in the structure of photonic crystal lattice is calculated. The results show that using the unique structure of the designed photonic crystal, which has defects in the lattice, the performance of the AND and NOT logic gates can be well observed.

By using the transfer matrix method, the optical properties of two one-dimensional tunable photonic crystal structures are investigated and compared with each other. The structure of the first photonic crystal consists of alternating layers of two dielectrics SiO2 and Si, with graphene layers between the dielectric layers. By adding polystyrene polymer as the defect layer to the photonic crystal structure, the defect mode appears within the photonic bandgap. This defect mode is tunable with the chemical potential of graphene and the wave incidence angle. In the structure of the second photonic crystal, one of the dielectric layers of the first crystal structure has a linear gradation. The defect mode is plotted for three structures with different linear gradation thicknesses and compared with the non-graded. The location of Defect modes in the crystal structure with linear graded in comparison with non-graded, shifts to lower frequencies. In both structures, the effect of the chemical potential of graphene and the incident angle of the transverse electric and transverse magnetic waves on the tuning of the location of the defect mode and photonic bandgap and graphene photonic bandgap are investigated. By increasing the chemical potential of graphene and the wave incidence angle, the location of the defect mode shifts to higher frequencies. These two structures can be used in designing the tunable terahertz filters