مجله فیزیک کاربردی
سال سیزدهم شماره 1 (پیاپی 32، بهار 1402)

In this work, the planar waveguides are investigated by depositing a SU-8 polymer on PET and quartz substrates. Maxwell equations are solved for the designed waveguides to obtain the characteristic equations. By solving these equations, the minimum thickness of SU-8 necessary for operation as a waveguide is found. Afterward, the waveguides are fabricated and characterized by profilometry and UV-Vis-IR spectroscopy. It is observed that SU-8 polymer shows suitable optical transmission. Then, the effective refractive index of the waveguide, as well as the wave propagation, is recognized by the finite element method. The results of simulations show that the total reflectance phenomenon that is required for a waveguide operation is occurring more effectively in the PET/SU-8 device than in the Quartz/SU-8 and in a waveguide configuration, it possesses better performance. Also, the flexibility and low cost of PET make it a proper candidate for substitution of the typical rigid substrate such as quartz.

In this paper, the optical properties of GaP in different phases have been investigated. The calculations were performed by using pseudopotential in the framework of density functional theory and using the PWscf code. The pseudopotentials applied here are generated using norm-conserving conditions within GGA for the exchange-correlation function. The optical properties of the Zincblend and Cinnabar phases reveal the conformity between the band structure and the imaginary part of the dielectric function, and the band gap and optical gap are almost equal. The refractive index obtained from the real part of the dielectric function in Zincblend is 3.306 and in the Cinnabar phase is 4.235 and 3.808 in the x and z directions, respectively.

The effective Hamiltonian describing indirect exchange interactions of type Ruderman- Kittel-Kasuya-Yosida [RKKY] between the magnetic impurities near the Dirac Points is based on the first-order energy. Besides, the points where the impurities are located are important in identifying the oscillatory behaviour of these interactions. Then in this paper, we first intend to obtain the effective Hamiltonian elements near the Dirac points for 2D graphene structures using the tight-binding approximation and then the phase factors between neighbor Dirac points are noticed. The obtained results are extended to obtain the effective Hamiltonian and then the first-order energy for carbon nanotubes. Using the quantized wave vector in the circumferential direction of nanotubes at Dirac Points, we examine the condition for nanotubes to be metallic or semiconductors. The obtained results based on the tight binding could be used to study the magnetic interactions at low energy for graphene structures as well as carbon nanotubes.

The transport properties of the Dirac fermions through the electric and magnetic barriers on the surface of a 3D topological insulator with a hexagonal warping effect have been investigated using the transfer matrix method. It was found that the transmission probability and the electric conductance are strongly modulated by the gate voltage, incident energy, number of barriers, and the exchange field strength. It was remarkable that the Dirac fermion is not perfectly transmitted at the normal incidence, confirming the role of the proximity effect in the suppression of transmission for normal incident electrons. The magnetic field can open up a band gap in the conductance spectrum at the Dirac point, depending on the magnetization orientation. The time-reversal symmetry remains broken as long as the magnetization orientations in modulated regions are not entirely parallel to the surface of a topological insulator. The resonant states and the position of resonant peaks are dependent on the gate voltage and incident energy values. It is shown that the number of tunneling resonances increases with increasing the number of barriers. The hexagonal warping effect can increase electronic transport at high energies. The results found here are consistent with those obtained previously.

This paper uses the Jaynes-Cummings model to investigate the entanglement of a two-qutrit state in a cavity. The entanglement is analyzed as a function of decoherence rate, coupling constant, and frequency of atomic transition. We note that this entanglement is decreased passing time and the negativity is an increasing function of the frequency of atomic transition. The negativity at first is an increasing function of the coupling constant, then for higher values of the coupling constant, the negativity decreases with the increase of the coupling constant and over time it tends to zero. We also investigate the influence of intrinsic decoherence on quantum teleportation via this two-qutrit state. We plot the fidelity as a function of the decoherence rate, the coupling constant, and the atomic transition frequency. The results show that the fidelity decreases with an increasing decoherence rate. Moreover, the frequency of fidelity oscillations is an increasing function of the atomic transition frequency. The fidelity is relatively independent of the coupling constant, especially at a higher value of the coupling constant.

The presence of heavy metal ions dissolved in tap water poses serious problems for human health. With the rapid growth of the world's population, the need to improve current technology for water purification and in order to provide safe drinking water is constantly increasing. Compared to various conventional heavy metal removal methods, cyanobacteria-mediated heavy metal removal is a more advantageous method, because of the cost-effective, on-site, and green chemistry approach. Cyanobacteria are a very suitable tool for the sequestration of metals because they can simultaneously divide the metal through biosorption and bioaccumulation. Bioabsorption is a cell surface occurrence, while bioaccumulation occurs inside the cell. In addition, the use of plasma technology as a driving force increases the percentage of metal removal in different periods. To write this article, a detailed search was carried out from the authors' experiences and articles and the latest articles available in PubMed, Web of Science, Google Scholar, ScienceDirect, Scopus, Medline, and Scientific Information Database databases. A review of the available articles showed that although there are many studies on the use of cyanobacteria in the removal of heavy metals, their combined use with plasma technology in biological treatment has been less studied. As a result, the purpose of this article is to review the separation of cyanobacteria in heavy metal ions from wastewater and the defense mechanism of cyanobacteria against metal-induced toxicity. In addition, we attempt to compare the ability of different species of cyanobacteria to separate heavy metals from water under different environmental conditions by producing exopolysaccharides and biosynthetic pathways. The results of this study can provide a complete picture of the identification and implementation of an applied bioremediation technique on an industrial scale that is cost-effective and environmentally sustainable.