Journal of Optoelectronical Nanostructures
Volume:5 Issue: 3, Summer 2020

In the present work, a theoretical analysis of the first-order of stimulatedBrillouin scattering (SBS) in a double-clad (DC) ytterbium (Yb)-doped silica fiber laserin unidirectional pumping mode is presented.An accurate simulation for calculating SBS nonlinearity is performed by considering thecoupled differential rate equations for pump, signal and Stokes powers, as well aspopulation inversion under the initial and boundary conditions in a typical all fiberbasedlaser with kW-range.In order to improve the laser operation and increase the laser efficiency, the dependenceof different parameters of the laser cavity such as active fiber length, fiber corediameter, dopant concentration, output mirror reflectivity at signal wavelength, as wellas the laser linewidth on the Brillouin threshold power has been studied.In addition, numerical analysis has been compared with the approximate analyticalsolution presented to emphasize the validity of modeling.As a result, the proposed laser design can generate up to 2.5 kW of output powerwithout the onset of SBS.

Supercapacitors have attracted much attention in the field of electrochemicalenergy storage. However, material preparation and stability limit their applications inmany fields. Herein, a reduced graphene oxide@phosphorus (rGO@P) electrode wasprepared using a simple inexpensive method. The new graphene structure (rGO@P) wascharacterized by X-ray di􀀀raction, Fourier transform infrared spectroscopy, scanningelectron microscopy and Energy-dispersive X-ray spectroscopy.Electrode showed excellent performances (307 F g−1), which seem to be the highestamong many other rGO@P-based electrodes reported so far. It also has an excellentcyclic stability up to 95% after 600 consecutive charge/discharge tests. So, the ease ofthe synthesis method and excellent performance of the prepared electrode materials mathave significant potential for energy storage applications.

There can be no doubt that nanotechnology will play a major role in our futuretechnology. Computer science offers more opportunities for quantum andnanotechnology systems. Soft Computing techniques such as swarm intelligence, canenable systems with desirable emergent properties. Optimization is an important anddecisive activity in structural designing. The inexpensive requirement in memory andcomputation suits well with nanosized autonomous agents whose capabilities may belimited by their size. To apply in nanorobot control, a modification of PSO algorithm isrequired. Using birds’ classical conditioning learning behavior in this paper, particles willlearn to perform a natural conditional behavior towards an unconditioned stimulus.Particles in the problem space are divided into multiple categories and if any particle findsthe diversity of its category in a low level, it will try to move towards its best personalexperience. We also used the idea of birds’ sensitivity to the space in which they fly andtried to move the particles more quickly in improper spaces so that they would depart thespaces. On the contrary, we reduced the particles’ speed in valuable spaces in order to domore search. The proposed method was implemented in MATLAB software andcompared to similar results. It was shown that the proposed method finds a good solutionto the problem regardless of nondeterministic functions or stochastic conditions.

We have studied the electron exchange-correlation effect on thecharacteristics of the two-component unmagnetized dense quantum plasma withstreaming motion. For this purpose, we have used the quantum hydrodynamic model(including the effects of a quantum statistical Fermi electron temperature) for studyingthe propagation of an electrostatic electron plasma waves in such that plasma consistingof quantum electrons and immobile ions. It is found that by regarding the latter effect, itpossible the excitation of two distinct modes. Some different cases such as:unmagnetized, collisionless, classical cases and some formulas presented and discussed.By using the reduced quantum hydrodynamic (QHD) model, the Korteweg de Vries(KdV) equation incorporating the electron exchange-correlation effect is derived. It wasshown that the electron exchange-correlation phenomenon on the main quantities for bothrarefactive and compressive types of solitary-wave propagation can be important. Inparticular, the arbitrary amplitude of electron solitary-wave experiences a spreading asthe effect of exchange-correlation becomes effective. Variations of the width of theelectron solitary wave for different plasma values were depicted. It was shown that byincreasing the exchange values, the width of soliton decrease.

Raman amplification of a 49 cm Bismuth oxide (Bi2O3) as a nonlinear gainmedium based erbium doped fiber amplifier (EDFA) is reported in new and compactdesign in near infrared spectral regions. The bismuth glass host provides theopportunity to be doped heavily with erbium ions to allow a compact optical gain fiberamplifier design by using reduced fiber length and the 1480 nm low pump poweraround 150 mW. A extended Raman amplification bandwidth of 45 nm, from 1520-1565 nm (C-band window) wavelengths is empirically proposed in a backward anddualwavelength pumped Bi-EDF by employing 350 mW Raman pump in 1440 nm.Because of the short length gain medium as a nonlinear Bi-EDF, amplification of 3 dBis achieved over a C-band wavelength range. This simple C-band Raman amplifierbased Brillouin and ASE backscattering was constructed to test the forward, backwardand dual-wavelength pump laser and on-off gain. A peak gain of 1.53 dB was obtainedwith a 3-dB bandwidth of 45 nm that the varieties of gain is 2.02 dB around 1545 nm inbackward pumping design. It array will be employ for sensing, spectroscopy andtelecommunication systems.

The present study was conducted to investigate current density of0.3 0.7 Al Ga N/ GaN multiple quantum well solar cell (MQWSC) under hydrostaticpressure. The effects of hydrostatic pressure were taken into account to measureparameters of 0.3 0.7 Al Ga N/ GaN MQWSC, such as interband transition energy, electronholewave functions, absorption coefficient, and dielectric constant. Finite-differencemethod (FDM) was used to acquire energy eigenvalues and their correspondingeigenfunctions of 0.3 0.7 Al Ga N/ GaN MQW and hole eigenstates were calculated througha 66 k.p method under an applied hydrostatic pressure. It was found that the depth ofthe quantum wells, bandgaps, band offset, the electron, and hole density increases withthe hydrostatic pressure. Also, as the pressure increases, the electron and hole wavefunctions will have less overlap, the amplitude of the absorption coefficient increases,and the binding energy of the excitons decreases. Our results showed that a change inthe pressure up to 10 GPa caused absorption coefficients҆ peaks of light and heavy holesto shift to low wavelengths of up to 32 nm, which in turn decreased short-circuit currentdensity and increased open circuit voltage.

This paper deals with the design and simulation of all-optical 4×2 encoderusing the wave interference effect in photonic crystals. By producing 4 opticalwaveguides as input and two waveguides as output, the given structure was designed.The size of the designed structure is 133.9 μm2. The given all-optical encoder has acontrast ratio of 13.2 dB, the response time of 0.45 ps, and also the bit transfer rate of2.2 Tbit/s. The results from these structures suggest the high flexibility of the structures,their resolution rates, and appropriate response time relative to that of other structures inthis rank as well as their applicability in terms of dividing. To elicit the optical band gaprage for structure design, the plane wave expansion method and also thefinite difference time domain methods were used to investigate the results fromdesigned structures.