فهرست مطالب

Optoelectronical Nanostructures - Volume:4 Issue: 3, 2019
  • Volume:4 Issue: 3, 2019
  • تاریخ انتشار: 1398/05/10
  • تعداد عناوین: 7
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  • Farideh Hakimian *, Mohammad Reza Shayesteh, Mohammadreza Moslemi Pages 1-16
    With the advancement of nanoscale semiconductor technology,semiconductor optical amplifiers are used to amplify and process all-optical signals. Inthis paper, with the aim of calculating the gain of quantum dot semiconductor opticalamplifier (QD-SOA), two groups of rate equations and the optical signal propagatingequation are used in the active layer of the device. For this purpose, the relatedequations are presented coherently. In our model, the rate equations that are ordinarydifferential equations (ODE) are solved by the Runge-Kutta method. The rate equationsare based on the occupation probabilities of the energy levels instead of the carrierdensities. On the other hand, the signal propagating equation is a partial differentialequation (PDE) and is solved by using the SLICE technique. Therefore, a suitablesolution for numerical modeling is presented. Based on the presented method, modelingis implemented in the MATLAB environment. The modeling results show a remarkableaccuracy of the model. Also, the proposed model is simple and the runtime is too shortin comparison with other similar models.
    Keywords: Numerical Modeling, Gain, Optical Amplifier, Quantum Dot Semiconductor
  • Omid Talati Khoei, Reza Hosseini * Pages 17-32
    A new side-contacted field effect diode (S-FED) structure has beenintroduced as a modified S-FED, which is composed of a diode and planar double gateMOSFET. In this paper, drain current of modified and conventional S-FEDs wereinvestigated in on-state and off-state. For the conventional S-FED, the potential barrierheight between the source and the channel is observed to become larger and the flow ofinjected electrons is reduced. Thus, the drain current decreases in on-state. While in offstate,the potential barrier height and width become smaller in conventional S-FED andso the drain current is greater than that of modified structure. Mixed mode simulationswere used to determine the performance of the proposed logic gates. We compared theoperation of modified S-FED with that of conventional S-FED. Simulated power delayproduct (PDP) of the modified S-FED-based NOR, NAND, XOR gates were found tobe about 416fJ, 408fJ and 336fJ, respectively, compared with 906fJ, 810fJ and 705fJachievable with conventional S-FED logic gates.
    Keywords: Logic Gates, Off-State, On-State, Propagation Delay, Static Power Dissipation, Power Delay Product
  • Bahareh Boroomand Nasab, Abdolnabi Kosarian *, Navid Alaei Sheini Pages 33-46
    Zinc oxide nanostructures are deposited on glass substrates in the presenceof oxygen reactive gas at room temperature using the radio frequency magnetronsputtering technique. In this research, the effects of zinc oxide sputtering pressure on thenanostructure properties of the deposited layer are investigated. The deposition pressurevaries from 7.5 to 20.5 mTorr. AFM results show that with an increase in the depositionpressure, the grain size increases and the surface roughness decreases. The energy gapmeasured for the zinc oxide layers deposited at the pressures of 7.5, 14 and 20.5 mTorrwas 3.26, 3.18, and 3.19 eV, respectively. In order to investigate the junction betweenzinc oxide and poly (3, 4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS),a polymeric layer of thickness of 50 nm is deposited on a 300 nm zinc oxide layer byspin coating technique. The dark I-V characteristics indicate that the reverse saturationcurrent density is 1.82 10-6, 1.96 10-7 and 7.58 10-8 A/cm2 for the depositionpressures of 7.5, 14, and 20.5 mTorr, respectively. By increasing the deposition pressurethe ideality factor of the resulting Schottky barrier dropped from 3.4 to 1.7. Theeffective Schottky barrier height of 0.73, 0.78, and 0.81 eV was obtained for the sameorder of deposition pressures. It was found that the highest optical response could beobtained for the samples deposited at the deposition pressure of 14 mTorr..
    Keywords: Ideality Factor, PEDOT:PSS, Radio Frequency Magnetron Sputtering, Schottky Barrier, Zinc Oxide
  • Mohammadreza Askaripour Lahiji *, Ali Abdolahzadeh Ziabari Pages 47-58
    The electronic, and optical properties of rhombohedral Na0.5Bi0.5TiO3nanostructured thin film have been studied by the first–principle approach. Densityfunctional theory (DFT) has been employed to calculate the fundamental properties ofthe layers using full–potential linearized augmented plane–wave (FPLAPW) method. A2×2×1 supercell was constructed with two vacuum slabs on top and down of thesupercell. A geometry optimization was performed by PBE method. The optimized thinfilm structure was used for the intended calculations. As well, the reflectance, dielectricfunction, refractive index, of the thin film were calculated in the UV–vis region. Resultsshowed very well consistency with the available experimental and theoretical reports.The optical conductivity also followed a similar trend to that of the dielectric constants.Energy loss function of the modeled compound was also evaluated. The evaluated lossfunction showed sharp peaks in UV-vis region and followed a steady state in IR, MIRand FIR parts of spectrum.
    Keywords: Band Structure, DFT, Na0.5Bi0.5TiO3 Thin Film, Optical Properties
  • Seyyed Mohammad Hosein Jalali, Mohammad Soroosh *, Gholamreza Akbarizadeh Pages 59-72
    In this paper, a photonic crystal structure for comparing two bits has beenproposed. This structure includes four resonant rings and some nonlinear rods. Thenonlinear rods used inside the resonant rings were made of a doped glass whose linearand nonlinear refractive indices are 1.4 and 10-14 m2/W, respectively. Using Kerr effect,optical waves are guided toward the correct output ports. In this study, plane waveexpansion and finite difference time domain methods were used for calculation ofphotonic bandgap and simulation of optical wave propagation, respectively. The size ofthe proposed structure is 1585 μm2 which is more compact than the previous works.Furthermore, the obtained maximum delay time is about 2 ps that is proper to highspeedprocessing. The normalized output power margins for logic 0 and 1 are calculatedas 25% and 71%, respectively. According to the obtained results, this structure can beused for optical integrated circuits.
    Keywords: Comparator, Kerr effect, Optical devices, Photonic crystal
  • Ghazaleh Ramezani *, Bizhan Honarvar, Masoomeh Emadi Pages 73-94
    A new modified magnetic Graphene Oxide with Chitosan and Cysteine wassynthesized for removing Pb2+ ions from aqueous solution. The properties of thisadsorbent were characterized by Field Emission Scanning Electron Microscopy (FESEM),Vibrating Sample Magnetometer (VSM) and Energy Dispersive Analysis Systemof X-ray (EDAX). Physicochemical parameters such as effect of pH, contact time,adsorbent dosage and initial concentration of Pb 2+ was also studied. The results showedthat the maximum capacity of absorbent in Lead ions adsorption (at Equilibriumconcentration of 120 ppm) occurred at pHOptimum= 5.75, tOptimum= 30 min andadsorbent 85.4 mg/g dosage=0.1 gr. Maximum empirical adsorption capacity (qmax) wascalculated 85.4 mg/g. The thermodynamic parameters (ΔHᵒ, ΔGᵒ and ΔSᵒ) showed thatthe adsorption process of Pb 2+ on modified magnetic Graphene Oxide with Chitosanand Cysteine was endothermic and spontaneous. Removal percentage was reduced to15% after five stages of Sorption/desorption studies. So, modified magnetic GrapheneOxide with Chitosan and Cysteine can be used as a complementary process for removalof Pb2+ ions from water and wastewater.
    Keywords: Magnetic Graphene Oxide, Surface modification, Nanoparticles, Removal of lead, Adsorption thermodynamics
  • Mohsen Olyaee *, Mohammad Bagher Tavakoli, Abbas Mokhtari Pages 95-116
    This paper proposes a full adder with minimum power consumption and lowloss with a central frequency of 1550nm using plasmonic Metal-Insulator-Metal (MIM)waveguide structure and rectangular cavity resonator. This full adder operates based onXOR and AND logic gates. In this full adder, the resonant wave composition of the firstand second modes has been used and we have obtained a high transmission coefficientin the states in which the output must be active. This full adder uses the AND and XORlogic gates to be designed with three inputs, which results in the design of a full adderwith lower complexity, lower cost and fewer losses than Other full adders in whichAND and XOR logic gates are combined to be designed with two inputs. The relatedsimulations were performed by FDTD. The obtained results presented a performancesimilar to the predicted models, while considering approximations with theoreticalrelations.
    Keywords: Cavity Resonator, MIM Waveguide, full-adder