نشریه اپتوالکترونیک
سال دوم شماره 1 (پیاپی 5، تابستان 1396)

Today, graphene nanostructures have made potential application in nonlinear optoelectronic devices, e.g. in narrowband filters. In this paper, the nonlinear absorption of one-dimensional defective photonic crystal made of Ta2O5 and SiO2 periodic layers and graphene layer as a structural defect showing non-linear optical properties are investigated in the visible wavelength region using the transfer matrix method (TMM). Due to the high third-order nonlinear susceptibility of the graphene layer, the optical Kerr effect is found to be a dominant effect in the studied structure. Results indicate that the absorption response of the structure is tuneable through the changes in periodicity, polarization and angle and amplitude of incident. Calculation results show that it is possible to achieve two absorption values of 0.99 with an incident amplitude of less than  and zero with incident amplitude higher than , an incident wavelength of 818 nm.

In this paper, Z-scan technique was used for investigating the effects of media polarity and concentration on the third order nonlinear optical properties of azo dye solutions. In this case, a cw mode laser at the wavelength of 650 nm and output power of 70 mW was used as a single excitation source. The experimental results indicate that reverse saturable absorption characteristics of the sample depend highly on the media polarity and concentration of dye solutions. According to the findings, by increasing the concentration of dye solutions, the nonlinear absorption coefficient of azo dye is increased in three different groups of solvents. High nonlinear absorption coefficients were observed in solvents with high hydrogen bond acceptor ability. Therefore, by selecting a proper solvent media and setting the concentration of dye solutions, a simple method for controlling the nonlinearity of selected azo dye was provided. Moreover, the selected azo dye with high nonlinearity and reverse saturable absorption characteristics can be used in optical devices.

In this paper, the electromagnetically induced transparency of an asymmetric quantum dot with Dresselhaus spin-orbit interaction and under the influence of external electric and magnetic fields is investigated. To study electromagnetically induced transparency, the dependence of absorption coefficient and refractive index of the probe light pulse on the Dresselhaus spin-orbit interaction strength, the electric and magnetic fields and dot size are measured and studied. The results show the considerable effects of Spin-Orbit Interaction and other mentioned parameters on the electromagnetically induced transparency of the system. It is possible to control electromagnetically induced transparency of typical systems via Spin-Orbit Interaction along with external fields and dimension.

In this experimental work optical nonlinear properties of aqueous solution of oxazine 1 dye and solutions containing of Ag nanoparticles were studied. For this purpose four samples as 0.2 mM aqueous solution of dye and solutions of dye containing 200, 300 and 400 ppm of colloidal Ag nanoparticles were prepared. All the aqueous samples showed a negative nonlinear refractive index of the order of 10-8 cm2/W. It was found that adding nano-particles decreases nonlinear refractive index of solutions. Also, nonlinear absorption of the samples were studied using open z-scan method. It was obsorved that in the pure aqueous solution of dye reverse saturation absorption is dominant mechanism of nonlinear absorption and adding silver nanoparticles decreases reverse saturation absorption of samples and increases saturation absorption of them. It seems that these differences in nonlinear properties were due to reduction of molecular aggregation of dye in water in presnce of silver nanoparticles.

The aim of this paper is the investigation of the optimal dense coding at the Jaynes -Cummings model as a quantum channel. First, with the introduction of the model we discuss a brief description of the dense coding. Then, by calculating the capacity dense coding, we investigate the effect of cavity Fock state in optimal dense coding. We show how the Jaynes-Cummings model, which is the result of the interaction of the field and the atom, can be located as an effective quantum channel in optimal dense coding.

In this paper, the formulation of spin coherent state in the real parameter in SU(1,1) group is studied. This representation of the coherent state is used for measuring the integral path and its classical consequence in the physical system. Using the completeness relation of the coherent state, we derive a path integral expression for transition amplitude and in the classical limit, we solve the classical equation of motion. Then, Lagrangian, equations and dispersion relation describing one-dimensional exchange anisotropic Non-Heisenberg model in the Anti-ferromagnetic system for dipole branch are calculated.

Nanocrystals have an important role in improving the mechanical and magnetic properties of different alloys. One of the most popular methods to get nanocrystals is the production of amorphous alloys. With suitable thermal annealing, one can form nanostructure in the amorphous matrix. In this research, amorphous alloy with composition Fe68Co26Si1C5 is prepared by melt spinning method. Then the prepared specimen was annealed at 400˚C temperature for 30, 60, 90 and 120 minutes. The structure of specimens before and after annealing is studied by using Mossbauer Spectroscopy, XRD. SEM,VSM, Microhardness tester.The obtained results show that some nanocrystals are created in the specimen with annealing.The specimen annealed during 90 minutes showed better properties because with the appearance of α –FeCo nanocrystalline phases, it was harder and denser and its hardness reached its maximum value, that causes the correction and promotion of mechanical and magnetic properties.