فهرست مطالب

Optoelectronical Nanostructures - Volume:4 Issue: 4, 2019
  • Volume:4 Issue: 4, 2019
  • تاریخ انتشار: 1398/09/10
  • تعداد عناوین: 7
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  • Ardalan Fatahizadeh *, Ardeshir Rabeie Pages 1-14
    We study an entangled two-mode coherent state within the framework of2×2-dimensional Hilbert space. We investigate the problem of quantum teleportation ofa superposition coherent state via an entangled coherent channel. By three differentmeasures with the titles ``minimum assured fidelity (MASF)”, ``average teleportationfidelity” and ``optimal fidelity (f)” we study the quality of this kind of teleportation.Decoherence properties of the entangled coherent state due to channel losses areanalysed. For a symmetric noise channel, the degradation of optimal fidelity and degreeof entanglement are calculated. Also by two different measures with the titles``concurrence” and ``entanglement of formation” we study the amount of entanglementof a decohered quantum channel and discuss its details. We demonstrate thatentanglement of the decohered entangled coherent state is reduced but not throughlylost. Finally we find that the optimal fidelity of the decohered entangled coherent state ismore than the classical limit and the decohered entangled coherent state may be usefulfor quantum teleportation.
    Keywords: Coherent states, Teleportation, Fidelity, Concurrence
  • Somayeh Fotoohi *, Saeed Haji Nasiri Pages 15-38
    Spin-polarized electronic and transport properties of Armchair GraphdiyneNanoribbons (A-GDYNR) with single vacancy (SV), two types of configurations fordouble vacancy (DV1, DV2) and multi vacancy (MV) defects are studied by nonequilibriumGreen’s function (NEGF) combined with density functional theory (DFT).The results demonstrate that the A-GDYNR with the SV has the lowest formationenergy and the most energetically favorable. The SV induces a 2.08 μB magneticmoment while the DV2 possess no magnetism into A-GDYNR. Analyzing the bandstructures shows that the perturbation in A-GDYNR caused by the SV, DV1 and MVbreaks the degeneracy and appears new bands around the Fermi level which indicate astrong spin splitting. Moreover, using density of states (DOS) analysis, it is illustratedthat the appeared flat bands correspond to the localized states which mainly contributeby the carbon atoms near the vacancies. The calculated current-voltage characteristicsfor A-GDYNR with the SV, DV1, and MV reveal that the spin degeneracy is obviouslybroken. As well, a high spin-filtering efficiency around 90% is found at the bias voltageof 0.3V for A-GDYNR with the SV. Our findings illustrate that we can obtain AGDYNRswith especial magnetic properties by removing carbon atoms from AGDYNR.
    Keywords: Graphdiyne, DFT, vacancy defects
  • Zeynab Bagheri, Mehdi Hosseini *, Omid Reza Daneshmandi Pages 39-52
    The variation of the electrical resistivity of a material in the externalmagnetic field is known as magneto resistance. This phenomenon has been attractedboth theoretical and experimental researchers in miniaturization of magneto meters inthe recent years. In this paper, the magneto resistance of an inhomogeneous twodimensional conductor with ladder geometry is simulated by using a two dimensionalresistor network model. Maxwell's equations have been solved for a point of latticeconsidered as disk and then, its magneto resistance was calculated using a networkmodel. The results illustrate that the magneto resistance depends on the specificresistance ratios and their locations. Moreover, the results demonstrate wheninhomogeneity is added properly, the magneto resistance will be increased, otherwise itwill be reduced. The results also show that for special values of physical parametersespecially the inhomogeneity, the magneto resistance is diverged at special magneticfield.
    Keywords: Magnetic Sensor, Giant Magneto Resistance, Resistor Network Model
  • Mahdi Zavvari *, Yashar Zehforoosh Pages 53-64
    An experimental study over the optical response of thin MoS2 films grownby chemical bath deposition (CBD) method is presented. As two important factors, theeffect of bath temperature and growth time are considered on the photocurrentgeneration in the grown samples. The results show that increasing the growth time leadsto better optical response and higher difference between dark and photocurrent. Forhigher bath temperatures the layer loses its uniformity and the current reduces. Betterperformance of optical response is obtained for t=90min and T=70oC. We also studiedthe effect of post-annealing on the performance and quality of thin films. The I-Vmeasurements show no current flow for annealed films because of rupture of the filmstructure. Temporal response of the films to light source ON and OFF states is alsostudied and the results showed relaxation of photocurrent after about several seconds.The importance of the MoS2 thin films obtained by CBD method is low-temperatureprocess and large area of fabricated layers which can be used in many applications.
    Keywords: Transition metal dichalcogenide, Molybdenum disulfide, Chemical bath deposition, Photocurrent
  • Mohammad Reza Mohebbifar *, Mehdi Zohrabi Pages 65-80
    In this study, a new approach for simulation of electric field enhancement ofplane wave laser around optical antenna was used to convert free-propagating opticalradiation to localized energy. A tapered gold tip design as a novel geometry of opticalantenna is introduced and numerically analyzed based on particle swarm optimization(PSO) by solving the Maxwell equations with FDTD simulation Lumerical Software.Five simulation stages of grating parameters to reach the maximum output intensity atthe gold tip hot spot were performed with 90° laser incident angle. The optimal valuesof the grating period “a”, distance of the last circular grating from tip apex “b”, depth ofetched grating “T” and duty cycle of grating “D.C” were obtained a=262.2 nm, b=759.5nm, T=30.1 nm, and D.C.=0.31 respectively. By using these optimal parameters for thegold tapered tip with a cone angle of 30° at room temperature, the maximum outputintensity (|Emax|2) at the hot spot was obtained 52.4751.
    Keywords: Optical Antenna, Localized Plasmon, Particle Swarm Optimization (PSO), Gold Tip, Surface Plasmon, Field Enhancement
  • Masoomeh Saberi Lamraski, Saeed Babaee *, Seyed Mahdi Pourmortazavi Pages 81-98
    In this research, in order to coating PETN particles, nano-pigment of redlitholrubine B 57:1 (NLR) was used in a surfactant environment of cetyltrimethylammonium bromide (CTAB) using solvent/none-solvent (water-acetone) method. Afterstructural studies of PETN-NLR nanocomposite by infrared (FT-IR) and field emissionscanning electron microscopy-Energy dispersive X-ray (FESEM-EDX) methods,Taguchi statistical design method was used to investigation and optimization of lightreflectance of nanocomposite at 532 nm. The effect of four factors of NLRconcentration, solvent flow rate, surfactant type and surfactant concentration in threelevels on light reflection was investigated and analysis of variance (ANOVA) showedthat NLR concentration with the participation of 67.24 percent had highest effect.Optimal conditions to achieve a minimum light reflectance were obtained of NLR 5wt%, solvent flow rate 1 mLmin-1, surfactant of CTAB and surfactant concentration1×10-3molLit-1. The lowest light reflectance by analyzing the data variance for optimumconditions was estimated 4.67 ± 2.14%. Also the mean experimental result for lightreflectance of the nanocomposite under optimum conditions was obtained 5.54 percent.Follows, thermal behavior and vacuum stability of the optimal sample was investigatedthat the results, due to the no significance difference in the melting point and thethermal decomposition mechanism of the nanocomposite compared to pure PETN,indicating the compatibility of NLR and CTAB with PETN
    Keywords: Optical Properties, Coating, PETN, Thermal Kinetic Decomposition, Solvent-non solvent, Taguchi Statistical Design
  • Masoud Jabbari *, Mehdi Dehghan, Mohammad Kazem M Moravvej Farshi, Ghafar Darvish, Mohsen Ghaffari Miab Pages 99-112

    In this paper, we present a switch based on coupling and resonance in thegraphene plate and rings operating at 10 THz. This structure consists of several layers ofHexagonal Boron Nitride (hBN), SiO2 and P+Si, such that graphene plates and rings areinside the hBN layer. The terahertz wave is incident from the upper part of the switchand Surface Plasmons (SPs) are excited by the grating in the structure on the grapheneplate beneath the nano-aperture and moves towards the ports available on the left andright of the switch. At first, at the certain applied voltage, the SPs cross the left port andthis port is ON. With the increase in voltage and the change in the chemical potential,switching occurs and the SPs exit from the right and this port is ON while the left portturns OFF. The extinction ratio in this structure is 18dB and the size of the structure is1μm. Aforementioned benefits make this switch the best choice for using in integratedoptical circuits.

    Keywords: Bidirectional Switch, Graphene, Resonance, Chemical Potential