Journal of Optoelectronical Nanostructures
Volume:2 Issue: 3, Spring 2017

Despite the simplicity of the hexagonal graphene structure formed by carbon atoms, the electronic behavior shows fascinating properties, giving high expectation for the possible applications of graphene in the field. The Graphene Nano-Ribbon Field Effect Transistor (GNRFET) is an emerging technology that received much attention in recent years. In this paper, we investigate the device performance of Graphene Nanoribbon Field Effect Transistor (GNRFET) as a function of contact doping concentration and the gate insulator dielectric constant. The simulations are based on the Non-Equilibrium Green’s function (NEGF) method coupled with a two dimensional Poisson equation in the ballistic regime. We assume a tight-binding Hamiltonian in mode space representation. By applying proper symmetric source and drain doping concentrations, It is observed that the GNRFET with low doping concentration has higher transconductance, lower Subthreshold Swing, lower Off-current (Ioff), and higher ratioof On-current to Off-current (Ion/Ioff). Moreover, The GNRFET with high doping concentration has smaller quantum capacitance, higher intrinsic cut-off frequency, and lower gate capacitance in comparison with low doping GNRFET. As we know, Selection of a suitable gate dielectric constant is important in determining device performance. The results indicate that the GNRFET with high dielectric constant has higher transconductance, lower Off-current, higher On-current and higher ratio of Ion/Ioff in comparison with low dielectric GNRFET. Furthermore, the GNRFET with low dielectric constant has smaller capacitances in gate, drain and source. The GNRFET with high dielectric constant has lower Sub-threshold Swing.

Researchers in the field of simulation have been mainly interested in the question of how to increase the efficiency of solar cells. Therefore this study aimed to investigate CdS/CdTe solar cells by applying AMPS-1D software. The impact of semiconductor layers thickness on the output parameters of the CdS/CdTe solar cell is being analyzed and studied carefully, for example, fill factor, efficiency, the density of short-circuit current and open circuit voltage. To acquire the most efficiency estimation, a new tandem multi-junction structure is intended by using two solar cells connected back to back with each other and designed based on the results gained from the single-junction solar cells. Numerical simulations demonstrated that the highest CdS/CdTe efficiency is 31.8% which can be achieved whenever the p-CdS layer thickness is equal to 50 nm, and the n-CdS layer thickness is equal to 200 nm, while the thicknesses of the n-CdTe layer and p-CdTe layer are kept fixed equal to 3000 nm and 1000 nm, respectively

In this paper, the optical properties of gold nanoparticles investigated. For this purpose the scattering intensity of a laser beam incident on gold nanoparticles has been studied using Mie theory and their respective curves versus different parameters such as scattering angle, wavelength of the laser beam and the size of gold nanoparticles are plotted. Investigating and comparison of the depicted plots show that the scattering intensity increases with increasing gold nanoparticles size up to 100 nm and further increasing of nanoprticles sizes leads to oscillating like behavior in the intensity patterns. Several peaks emerges in the patterns of intensity versus nanoparticle size. It was also found that for particles with sizes less than 100 nm the intensity patterns versus wavelength had a one peak about 520 nm while for the particles bigger than 100 nm there appears other maxima in different wavelength too. Changing the angle of scattering led to change in the intensity pattern of scattered light and its minimum value was detected at 90°. These results can be used in detecting cancerous tumors and in cancer therappy.

The rouge waves in an optically injected semiconductor lasers are receiving a lot of interest. In this work, the generating and controlling of the rogue waves in semiconductor lasers have been investigated. For this purpose, the laser’s rate equations are solved numerically in a specified time interval, then the field amplitude and the intensity versus time are calculated and analyzed. To solve the rate equations, the famous finite deference method (FDM) is used. Also the rouge waves are counted using the standard definition that is mentioned in the context. Furthermore, the effects of the injection strength and the detuning frequency on the rogue wave’s occurrence are studied. Results show that by increasing the injection amplitude, the number of rogue waves decreases significantly, so that rouge waves vanish at the large values of the injection amplitude. Also increasing the detuning frequency, reduces the number of rogue waves and this reduction is more sensitive at the large injection amplitude.

Total internal reflection fluorescence microscopy (TIRFM) is an optical technique that allows imaging of a thin layer of the sample with a thickness of about 100-200 nm. It is used in science of cell biology to study cellular processes, especially near the membranes of living cells. This method is based on the total internal reflection phenomenon, where the evanescent wave is generated in the less dense medium. In fact, the evanescent wave is used to illuminate the sample. Consequently, the possibility of observing a superficial (instead of bulk) part of fluorophore labeled sample is opened up. In this work, a total internal reflection fluorescence microscope based on the light guide has been designed and assembled by means of the inverted microscope to image a thin layer from the surface of the sample. Operated experimental arrangement has been employed for the total internal reflection fluorescence imaging of cadmium selenide (CdSe) quantum dots.

In this paper we investigate focusing properties of graded index (GRIN) photonic crystal (PC) structures which are composed of different materials with different refractive indices. GRIN PC structure is constructed from air holes in dielectric background. The holes radii are varied in the normal direction to the propagation in such a way that a parabolic effective refractive index is produced. The focusing characteristic is studied relative to the refractive index variation of background material. While increasing refractive index of background material of the GRIN PC structure, the effective refractive index of the structure increases. With increasing effective refractive index, the focusing capability of the GRIN PC structure increase and outgoing wave at focal point will be more concentrated. The result shows that the designed GRIN PC structure work very well as a focusing lens. The finite-difference time-domain (FDTD) method was employed to compute field propagation through GRIN PC structure. Also, plane wave expansion (PWE) method has been carried out to extract the dispersion properties

PT-Symmetry is one of the interesting topics in quantum mechanics and optics. One of the demonstration of PT-Symmetric effects in optics is appeared in the nonlinear directional coupler (NLDC). In the paper we numerically investigate the stability of temporal bright solitons propagate in a PT-Symmetric NLDC by considering gain in bar and loss in cross. By using the analytical solutions of perturbed eigenfunctions and corresponding eigenvalues the stability of temporal bright solitons is studied numerically. Three perturbed eigenfunctions corresponding to the two eigenvalues are examined for stability. The results show that the two degenerate eigenfunctions are unstable while other one is stable which have important result that the eigenfunctions are equilibrium function but not stable for all cases. Stability is tested by using energy of perturbed soliton that propagate thought the length of NLDC. In addition, the behavior of solitons under instable perturbation in a PT-Symmetric NLDC can be used to design integrated optics at Nano scales, for ultrafast all optical communication systems and logic gates.