نشریه اپتوالکترونیک
سال پنجم شماره 1 (پیاپی 12، پاییز و زمستان 1401)

In this study, for the first time, the calculation and investigation of the qualitative behaviors of entropy and decoherence effects in quantum two-mode squeezed (QTMS) radar when the target is present and the generated signal is transmitted to the target is discussed. In general, incoherence is associated with a decrease in the purity of the state of the system, that is, the transition from a pure state to a mixed state. Additionally, by examining the entropy, we examine the entanglement of the system for the effective number of photons at the detector input. In addition, various conditions affecting the performance improvement of a quantum detector in QTMS radar are evaluated. The quantum state of the system changes from the coherent state to the incoherent state with the increase of temperature and squeezing parameter (at high temperatures). The decoherence effects are inversely proportional to the squeezing parameter and signal power. The ratio of received photons in the receiver is directly proportional to the squeezing parameter and signal power. Increasing the ratio of received photons in the receiver increases the entropy of the system and reduces the decoherence effects of the system, which is a very important result. Moreover, the qualitative behaviors of entropy and purity are quite similar.

In this paper, we model an entangled system of two identical superconducting qubits in which Josephson junctions are coupled by a fixed capacitor. This coupling of the capacitor with Josephson junctions is added due to increase the coherence and neutralize the effects of decoherence in the system. To better understand the state of the system, using the theory of quantum computing, the qualitative behaviors of entanglement, coherence, and comparison between them are numerically investigated. It was observed that there is a limit for increasing the mutual coupling energy between two qubits, and beyond that, it will weaken the system performance. It was also seen that the behaviors of the entanglement and the coherence are almost similar and they can be maintained at high temperatures under some conditions. A remarkable point was is that, as the Josephson energy of the qubits increases, the coherence and entanglement increase even at high temperatures. Also, by increasing the mutual coupling energy between qubits, coherence and entanglement are maintained at high temperatures, which can be considered in the construction of entanglement sources. In addition, the difference between an identical and a dissimilar two-qubit system is also stated.

The challenges in the miniaturization of photonic integrated circuits due to manufacturing problems and the phenomena that exist in nanoscale systems have caused plasmonic nanostructures and the application of plasmonic waves to attract a lot of attention. The use of liquid crystals in plasmonic devices helps to control the transmission, reflection, scattering and absorption of light waves in plasmonic nanostructures. In this article, the effect of liquid crystal on surface plasmon polariton properties in two cases: a) presence of liquid crystal, b) absence of liquid crystal at the common border of gold metal have been investigated. The results of this study show that gold nanostructures in the presence of liquid crystal can respond to optical light in a more active way, compared to an empty piece of liquid crystal. By shining light on the optical part, due to the strong interaction between surface plasmons at the common boundary of the two environments, we will have a intense absorption spectrum, which is observed in the form of a resonance peak at shorter wavelengths in the homotropic orientation of the liquid crystal. The resonance wavelength of surface plasmons is sensitive to changes in refractive index. In other words, by increasing the refractive index of the surrounding environment, the peak of the absorption spectrum shifts to longer wavelengths.

We have investigated the optical properties of the double-periodic structure containing graphene-based hyperbolic metamaterial using the transfer matrix method and the effective medium theory at the Terahertz frequency region. Our findings reveal that this structure may have multiple band gaps in hyperbolic and elliptical frequency regions. Moreover, it shows that the transmission and absorption for TM polarization depend on both graphene chemical potential and optical axis orientation of the hyperbolic metamaterial layers. However, in the TE polarization case, these optical properties only depend on graphene chemical potential.

In this paper, a new Graphene-based field effect transistor (FET) with resonant tunneling transport is introduced and modeled which is also applicable for many other non-graphene, flat two dimensional structures with energy gap. As like other graphene-based FETs, the current passes through semiconducting 2D GNR. But here by adopting P-type source and drain as well as a special geometry of gate contact, the GNR channel is turned into two coupled quantum dots in series. The coupling between Dots and sizes of Dots determine the current characteristic of the device. Resonant tunneling is observed in current-voltage characteristic of the device.

In this research, the structural features, electronic and magnetic properties of armchair (5, 5) indium phosphide nanotube doped with Cr, Co, Cu and Zn have been investigated using first principles calculations. Calculations were performed by the PWscf code using a density functional theory. The metals Cr, Co, Cu and Zn were replaced by P atomic position in this nanotube. The optimal angles between them and the bond length were calculated. The calculations illustrate that there is a structural distortion around Cr and Co impurities, and also show that the magnetic moments are consistent with the predicted value of Hund’s rule. Furthermore, the observations revealed that the indium phosphide nanotube doped with Cr and Co is a ferromagnetic metal, while the indium phosphide nanotube doped with Cu and Zn is a non-magnetic metal. The present results predict that indium phosphide nanotubes doped with Cr and Co are useful for industrial applications in Nano magnets. To identify the most stable configuration, the binding energy and the cohesive energy were calculated for all compounds. Finally, our results show that the InP nanotube doped with Cobalt is more stable than others

A surface plasmon resonance (SPR) sensor based on photonic crystal fiber (PCF) was designed and gold was used as a sensitive plasmonic layer. The performance of this sensor was investigated using the finite element method (FEM) for the refractive indices (RIs) of 1.39 to 1.43. This sensor had a sensitivity for the defined RIs ranging from 3936.5 to 67315 nm/RIU at the wavelength of 850 to 2650 nm and had the highest resolution, the best figure of merit (FOM), and amplitude sensitivity with the values of 1.486×10-6 RIU, 524.825 RIU-1, and 2300.57 RIU-1, respectively. Therefore, due to the simple structure of this sensor and its favorable performance, it can be used as a beneficial diagnostic tool for biological materials with different RIs.

Plasma is often refer to the fourth state of matter in science and it is created from a partially or completely ionized gas, which is consisted of ions and free electrons, atoms in the ground or excited state, and most importantly, photons in different energies, and is divided into two categories. They divide into equilibrium (thermal plasma) and non-equilibrium (low temperature plasma or CP). CP is suitable for operations on food products that are sensitive to heat. Creating a suitable cold plasma environment with Townsend's mechanism is related to the control of many physical factors such as the gap and type of electrodes and dielectrics, ambient pressure, frequency and applied high voltage. In this research, after designing and building a food disinfection device based on atmospheric cold plasma technology, the optimal distance of aluminum electrodes was calculated in the potential range of 4 kV to 12 kV. The results made it clear that at distances of more than 9 mm, the phenomenon of Streamer breakdown even at maximum potential causes the destruction of the plasma environment.

The electromechanical coupling behavior of composite piezoelectric materials plays an important role in various industries. Therefore, it is necessary to investigate and study the propagation and scattering of waves in such materials in order to understand their properties and dynamic behavior. in this study, using an exact analytical method, electromechanical fields due to the scattering of plane waves by a piezoelectric spherical particle with spherical isotropic embedded in an unlimited isotropic polymer matrix has been studied. In the present formulation, there is no restriction on the range of the frequency of the incident wave. The dynamic stress concentration factors and the dynamic electric displacement concentration factor at the piezoelectric particle-matrix interface were calculated. Subsequently, the effect of the frequency of the incident wave on the maximum values of the dynamic stress concentration factors and maximum value of the dynamic electric displacement concentration factor as well as their appurtenant locations for shear and longitudinal waves compared

This study aimed to investigate the effect of tissue-bone heterogeneity on the response of holographic interferometric calorimeter system by using modeling techniques. Interferometric calorimeters were widely used in medical applications for measuring temperature changes during thermal therapies. However, the presence of tissue-bone heterogeneity can affect the accuracy of these measurements. In this study, a computational model was developed to simulate the response of interferometric calorimeters in the presence of tissue-bone heterogeneity. The results show that tissue-bone heterogeneity can significantly affect the accuracy of temperature measurements made by interferometric calorimeters. Therefore, this study highlights the importance of considering tissue-bone heterogeneity when using interferometric calorimeters in medical applications.

In this research, the electronic, magnetic and optical properties of inverse Heusler alloys Ti2ScX (X=Si,Sn) were studied using the Quantum Espresso software package based on the density functional theory. The results of the electronic properties investigation showed that both alloys are half-metals in their equilibrium lattice constant and exhibit 100% spin polarization around the Fermi level. The indirect half-metallic band gap for Ti2ScSi and Ti2ScSn alloys were obtained as 0.35eV and 0.11eV, respectively. Furthermore, considering the high values of the Curie temperature of Ti2ScX (X=Si, Sn) alloys, it can be concluded that these alloys are stable at room temperature. Analyzing magnetic properties revealed that Ti2ScX (X=Si,Sn) alloys exhibit ferromagnetic behavior in their stable structure, and their total magnetic moment is 7µB/f.u., which is in good agreement with the Slater-Pauling rule. Consequently, it can be inferred Heusler alloys Ti2ScX (X=Si,Sn) are half-metal ferromagnetism. Additionally, the optical properties of these alloys suggest their potential as electromagnetic waves absorbers.

Jiles-Atherton model equations was used in many ways to describe the hysteresis loops of ferromagnetic, ferroelectric and piezoelectric materials. The main advantage of this model is establishing a connection between the hysteresis loop and the physical parameters of magnetic materials. In this study, the magnetic hysteresis curve was presented by using the finite element method and the COMSOL code. The Jiles-Atherton model equations was used to simulate the hysteresis loop, magnetic flux density and magnetic field components in the software. The purpose of this study, while examining the Jiles-Atherton model equations, is to know the effect of changes in the physical parameters of the magnetic material on the magnetic hysteresis curve. The obtained results indicate the changes in the area of the hysteresis loop, the characteristic values of this loop, the changes in the magnetic flux density and the components of the magnetic field by increasing or decreasing the parameters of the Jiles-Atherton model. The decrease in the area of the hysteresis loop and the decrease in the characteristic values of this loop is a reason for changing the behavior of the ferromagnetic material towards soft magnetization and reducing the interaction of the magnetic domains of the ferromagnetic material and vice versa.