Journal of Optoelectronical Nanostructures
Volume:5 Issue: 4, Autumn 2020

n this paper, the generation of a highly broadband supercontinuum spectrum has numerically been investigated in a suspended As2Se3 based ridge waveguide. By changing the dimensions of the proposed waveguide, the dispersion has been engineered to achieve a suitable profile with the two zero-dispersion wavelengths as well as the lower magnitude and flat anomalous dispersion regime. Due to the high refractive index contrast between the core and cladding, the propagated light has been highly confined in the core and as a result, a high optical nonlinear coefficient has been obtained. Simulation results show that when the pump pulses with a width of 100 fs and peak power of 1KW at the wavelength of 2150 nm are injected into the designed

CIGS solar cells are regarded to be one of the best thin film solar cells withefficiencies up to 22.6%, which exceeds the current multicrystalline Si record efficiency(21.9%). To make the promising CIGS solar cells more economic, reduction of costly Inand Ga elements through thinning of CIGS layer seems necessary. But, it causes the cellperformance degradation. This study is aimed to investigate the efficiency enhancementof ultrathin CIGS solar cells by using of Al plasmonic nanoparticles. Plasmonicnanoparticles can restrict, absorb, navigate or scatter the incident light. The role ofdifferent location of Al nanoparticles within the active layer was studied through opticaland electrical simulation utilizing FDTD and DEVICE solvers of Lumerical software.By using the spherical Au nanoparticles, the light absorption in the cell increaseddrastically. The highest ç=15.31% was achieved for the designed ultrathin CIGS solarcell decorated by Al nanoparticles located in the middle of the absorber layer.

Carbon spheres with controllable structures (i.e., nano and microstructure)were prepared by using a hydrothermal method. By adjusting the concentration ofglucose solution at a both constant temperature and constant process time in a sealedautoclave, the total size of carbon spheres (CSs) was changed from nano to microscale.Then micronanobinary carbon spheres structure (MNCS) was successfully obtained bycoating colloidal solution of carbon nanospheres (CNSs, average diameter of 186 nm)and microspheres (CMSs, average diameter of 5 μm) on the FTO substrates. It wasrealized that by annealing of the carbon spheres under vacuum condition, theirfunctional groups were reduced, therefore, this effected on the wetting behavior ofcarbon spheres. The effect of hierarchical roughness as a beneficial factor on thesuperhydrophobicity of CSs was analyzed by the investigation of the contact angle(CA). The highest CA was measured for the mixture structures containing both themicro and nanoscale spheres. Based on the new research, CA of the surface withmicronanobinary structure is larger than the nanostructure and the nanostructure islarger than the microstructure and above all, theoretical calculations confirmed theexperimental measurements.

In this paper, we propose a numerical model for Four-Wave Mixing (FWM)efficiency in quantum dot semiconductor optical amplifiers (QD-SOAs). Despite thecomplexities of the equations governing the QD-SOAs, simple models with shortcomputational time are essential to analyze and design them. We present equations ofthe QD-SOAs coherently and calculate FWM efficiency in the QD-SOA using thepump/probe technique. In this model, the rate equations take into account theoccupation probabilities of each level instead of the carrier of densities. Moreover, thetransfer matrix based on the pump/probe measurement technique is solved in twodimensions, space and time, using the Slice technique. The described model isimplemented in the MATLAB environment. The proposed model is simpler than similarmodels and has a shorter computational time than them

Structural, electronic, and optical properties of one-dimensional (1D) SnGe and SnC with two types (armchair and zigzag) and different widths are studied by using first-principles calculations. The atoms of these structures in edges are passivated by hydrogen. The results show armchair SnGe and SnC nanoribbons (A-SnXNRs, X=Ge, C) are the direct semiconducting and divided into three distinct families W=3p, W=3p+1, and W=3p+2, (p is a positive integer). By increasing width, the band gaps converge to 1.71 eV and 0.15 eV for A-SnCNRs and A-SnGeNRs, respectively. Furthermore, the position of the first peak of the dielectric function in both of them occurs in their value of direct band gap at Г point. also, the absorption coefficient for 9, 11, 13 A-SnCNRs displays that there is no absorption at the lower energy range from 0 to 1.2 eV, whereas absorption characteristics for 9, 11, and 13 A-SnGeNRs appeared at near-infrared to the visible spectrum. These results can provide important information for the use of Group IV binary compounds in electronic devices.

In this paper, the effect of strain on the efficiency of GaAs solar cell isinvestigated. It has been shown that the applied strain during the synthesizing of carbonnanotubes (CNTs) leads to changing some of its physical properties. This means that strainscan cause numerous changes in the structures. By using a strained layer of the carbonnanotubes on the GaAs solar cell, the effect of this layer on the performance of the GaAssolar cell is evaluated. This CNT layer can be used for several purposes. The first is tocreate a transparent electrical conductor at the cell surface to increase the output current.This purpose is one of the most important applications of this layer. But the second andmore important goal is to capture more photons and reduce the emission or reflection oflight emitted onto the cell surface. It is found that the mentioned goals cannot be satisfiedsimultaneously. Accordingly, to solve this problem, two different layers were used toachieve the ideal conditions. It has been shown that the use of a 10% uniaxial strained CNTlayer leads to increase the photon absorption rate onto a non-strained CNT layer forelectrical purposes. The efficiency of the single-junction GaAs solar cell with the aboveconditions reaches about 31% which is about 2% higher than the model without strain.

Influences of spin polarization on the electronic traits of undoped and MndopedLaCoO3 nano scale layers in the rhombohedral phase have been investigated inthis paper. First, we employed the local density approximation (LDA) method with thegeneralized gradient approximation (GGA) under density functional theory (DFT). Thecalculated results did not show an appropriate consistency with experimental values.Knowing the presence of 3d orbitals in Co atom, to taking account the stronglocalization of electrons, we used the local spin density approximation plus a Hubbardliketerm (LSDA+U). Calculations were performed using different U values at lowtemperature and the obtained results showed high consistency with the experimentalvaluesand the optimum results were obtained for U=1.The calculated band structuresalong with the partial densities of states (PDOS) shows the nonmagnetic nature ofLaCoO3 at low temperatures. Also, adding Mn has a significant effect on the electronicproperties of LaCoO3. It was revealed that Mn changes the nonmagnetic characteristicof the compound to the magnetic feature.The bandgap values for spin up (SU) and spindown (SD) states have been calculated 0.9 eV and 1.2 eV, respectively and both stateshave direct bandgap.