نشریه اپتوالکترونیک
سال ششم شماره 1 (پیاپی 14، پاییز 1402)

In this paper, the electrical transport properties of a quasi-one dimensional heterostructure based on the GaAs (such as quantum wire) are studied in the presence of the electron-phonon interaction, theoretically. In this regards, a homogeneous quasi-one dimensional quantum wire with a given length is considered which is coupled between two semi-infinite metal leads. Using the Hamiltonian of the system the framework of the tight binding method within the effective mass approximation, the electron transmission coefficient are studied as a function of the electron energy and also the applied filed frequency. Different values of the length as well as Al concentrations of the central region are considered. In order to investigate the electron-phonon effects, we consider a time and space dependent external field which is applied on each atoms in a linear chain within the harmonic approximation. The numerical results of this paper can have shed light on the electron-phonon impacts on the electron transport of the nanowire.

We introduce a trilayer permanent magnetic lattice for ultracold atoms which is created by two 2D arrays of square magnetic slabs plus a bias magnetic field. Three separate 2D arrays of magnetic microtraps located above the top layer of magnetic slabs, below the bottom layer and between them are produced. We provide analytical expressions for determining the location of non-zero magnetic field minima, as well as other physical quantities such as the absolute value of the magnetic field (B), curvatures, and trap frequencies at each minimum. The analytical expressions for B are in good agreement with the numerical results. Therefore, all the analytical expressions extracted from them are reliable. Some of the relevant physical quantities can be controlled using the bias magnetic field. Also, the trap frequencies between the magnetic layers in a trilayer lattice are higher compared to those in a bilayer lattice created by a single layer of magnets. Therefore, atom loss decreases and a better confinement is provided for them.

In this study, the electronic and magnetic properties of monolayer phosphorene through spin polarized density functional theory are investigated. The monolayer phosphorene is a p-type nonmagnetic semiconductor. Phosphorene has many applications in electronic devices such as transistors and ionic batteries, but no magnetic properties of pristine phosphorene limits its applications in spintronic devices. By applying antidote vacancy defect with 6 atoms vacancies, the sample becomes magnetic and this issue is resolved. For this purpose, we use a supercell of 64 atoms. In addition, the energy bandgap of the structure decreases from 1.50eV to 0.33eV by applying defect, and the structure transits to the n-type semiconductor. By H-passivating, the energy bandgap increases to the value 1.73eV. The semiconductor type of this sample returns to its initial type, p-type. With structural engineering, it is possible to design the sample with the desired bandgap energy and magnetic property, and fabricate in the Lab for the desired application.

Inductively coupled plasma (ICP) is widely used in applications such as material processing and microelectronic device fabrication. However, their electromagnetic properties have not been fully investigated. Therefore, we performed time-dependent (2D) finite element simulations in this study. We have made profiles of magnetic field, electron density, and temperature distribution for argon gas by applying variable power of 750 W, 950 W, 1100 W and 1200 W. In a comparative study, the effect of input power change on plasma parameters was investigated and the relevant results were shown. It was shown that with increasing power, the electron density and temperature in the working chamber increase. In the following, with a constant power of 1200 watts as an optimized power, the effect of changing the position of the coils and reducing the thickness of the dielectric layer on the magnetic field flux, electron density and temperature was investigated and we showed that by changing the position of the coils, the magnetic field flux, the electron density and the temperature of the reactor do not change. However, with the decrease in the thickness of the dielectric layer, the magnetic field flux, the electron density, and the temperature decrease to an insignificant amount.

In this study, a small electro-optic switch is designed and simulated by designing a plasmonic waveguide with high confinement. By using a silicon ridge near graphene and adjusting its chemical potential, a plasmonic channel is provided that controls the optical signals transmission depending on the graphene chemical potential. By applying chemical potentials of 0.1 eV and 0.5 eV, the channel loss for frequencies ranging from 25 to 45 THz changes from 78.03 to 0.23 dB/µm. The structure size is 0.057 µm2, which is smaller than similar structures. The small size of the structure is one of the fundamental requirements of optical integrated circuit designing. This feature, along with a coupling length of 218.2 µm and a figure of merit of 1246, indicates that surface plasmons are well confined and guided in the designed channel. With regard to the obtained results, the designed plasmonic switch can be proposed for various analog and digital applications.

In quantum thermal machines, by using a quantum working substance work can be produced. In a quantum Otto machine, if the difference between energy levels are changed by the same ratio in the adiabatic process, the efficiency of this machine is the same as its classical counterparts; However, if this difference is changed inhomogeneously, it will have larger efficiency. Additionally, by the use of non-thermal reservoir (squeezed thermal or coherent thermal) instead of thermal reservoir more work and efficiency can be produced. In this investigation, using a simple harmonic oscillator as the working substance in the quantum Otto machine and adding a delta barrier, in order to make the inhomogeneous difference in energy levels, also considering a non-thermal reservoir, the efficiency and work are investigated. The results show that by utilizing this working substance and non-thermal reservoir, will make efficiency and work to be increased in the special frequency interval.