مجله فیزیک کاربردی
سال سیزدهم شماره 4 (پیاپی 35، زمستان 1402)

The design of optical sensors in the THz region for application in various fields of biological and medical sciences has significantly expanded in the last two decades. In this paper, we proposed an optical sensor using two dimensional and periodic structure of graphene rings on the dielectric substrate. The surface plasmon resonance mechanism was employed to design the refractive index sensor. First, by changing the geometric parameters of the structure, the optimal parameters for the sensor performance have been extracted. Then, the sensor's sensitivity has been checked regarding the change in the refractive index of the surrounding environment. The sensitivity of the proposed simple structure is 11.2 μm/RIU and is larger than previous works. Also, increasing the refractive index of the measured medium diminished the quality of sensor operation. The proposed sensor can be used to detect environmental air pollution by proper calibration. The Lumerical software which is based on the finite difference time domain method is used to this end.

Analyzing the electromagnetic transition strengths is one of the methods of studying the development of atomic nuclei the big-bang, and the fuel cycle of stars in nuclear astrophysics, nuclear synthesis and radiative capture. The study of nuclei with mass number A=11, for example, 11B and 11C, is significant which can be produced by radiative capture of protons by 10B the dependence of the reduced transition probability related to electric quadrupole B[E2] and magnetic dipole B[M1] that occurs in proton radiative capture by 10B nucleus has been investigated. It depends on the excitation energy and spin-parity of the states for the occurrence of  E2 and M1 transitions. The theoretical framework of the calculations based On the Woods-Saxon potential model and double folding M3Y has been used to create the ground and excited states of 11C . The results obtained based on each of the mentioned potential models are in good agreement. It was found that B(E2) increases with the increase of excited energy regardless of the spin of excited states. At the same time, B(M1) is very sensitive to the spin of excited states, and also(3/2)-excited states are independent of the energy.

Solar winds result from the eruption of plasma streams from the solar corona. This plasma, which consists of proton particles, electrons, X-rays, and radio waves, penetrates the heliosphere and accelerates from the interplanetary space toward the Earth with high kinetic energy and thermal energy. In addition, if it collides with the Earth's atmosphere, it disrupts human life. But despite the Earth's magnetic field and the magnetic reconnection process in this area, the Earth's magnetosphere acts like a shield and prevents these substances from affecting the Earth. To obtain the necessary information to investigate all kinds of phenomena that happen around the Sun, the use of satellite data is the best and most reliable method in terms of accuracy and up-to-date data. The data from the Goes meteorological satellite, LASCO spacecraft, and the Solar Dynamic Observatory are the information that we use in this article to advance our goals. To check the correlation between solar eruptions and changes in the Earth's magnetosphere layer, we use the wavelet analysis method with Morlet's fundamental wave, which is an important tool for processing fluctuations. The results of accurate numerical calculations of this research showed that there is a strong correlation between the magnetic activities of the Sun and the characteristic indices of the Earth's magnetosphere layer, which can affect the Earth's atmosphere as well.

In this paper, using 2D PIC simulation, the electron acceleration in the bubble regime has been investigated in the interaction of a short high-power laser pulse with an underdense plasma with a density ramp. Due to the laser pondermotive force, a plasma wave and its corresponding electric field are formed in the plasma. The electrons injected in the focusing and acceleration region of the plasma wave field can get energy from the wave and are accelerated to high energies of the Giga-electron-Volt range. The simulation results show that with increasing the plasma density gradient, the phase speed of the generated plasma wave increases, and the corresponding wavelength decreases. This causes the displacement of the plasma wave focusing and acceleration region and ultimately increases the acceleration length in the acceleration process. Considering a laser pulse with dimensionless intensity amplitude , pulse duration , and plasma with density ramp length ,the plasma wave accelerating electric field with amplitude was generated. The results of this work can be crucial in choosing an appropriate plasma profile to design the laser-plasma accelerator system for obtaining the Giga-electron-Volt energy gain in a short time.

In this article, we will first get acquainted with the absorption and emission optical properties of algae and types of chlorophylls, and then we will examine the optical setup for measuring the photoluminescence light produced by algae, which is the basis for the construction of chlorophyll concentration measuring devices. By examining algae samples in fresh water ponds in Iran and identifying the predominant type of algae in them, spectrometry and concentration measurement were carried out with the help of hemocytometer or neobar lam method. The most important tool for measuring the concentration of algae is chlorophyll-a, which is present in all types of algae with different percentages and has the property of fluorescence, and by measuring the red light resulting from photoluminescence, the amount of chlorophyll-a can be obtained. The main design of a device to measure the amount of chlorophyll-a based on the measurement of photoluminescence light is considered for this purpose and it is used in terms of software and hardware. For this, the process and intensity of light in terms of density was done for calibration, and the disadvantages and advantages of the design were examined. Direct measurement of light, noises, high stability and preparing a logical routine between the data can help to increase and improve the quality and this device becomes a precise tool for measuring chlorophyll and has commercialization capabilities. The stability, reproducibility and high accuracy of the device is one of the advantages of emission (photoluminescence) test methods compared to absorbance methods.

This work aimed to theoretically investigate the operation of the beta voltaic battery with the 14C radio isotopic source and several semiconductors in the p-n junction structure. For this purpose, the saturated thickness of the 14C beta source and energy deposition distribution of beta particles emitted from this source is simulated and calculated in the various semiconductors including the GaAs, GaN, SiC, and diamond using the Monte Carlo code of MCNPX. Regarding the results obtained, the optimized 14C thickness was achieved by 30 micrometers. Then, applying the analytical and numerical model, the relationships between the doping concentration, short circuit current density, open circuit voltage, and output power density were evaluated. The results showed that with   and    with the diamond as semiconductor, the output power density of designed battery was increased to 9.68 among the other considered semiconductors.

In this research, linear and non-linear optical properties of silver oxide nanoparticles in graphene oxide medium have been investigated. First, graphene oxide is prepared by the improved method of Hammers. Then the synthesis of silver oxide nanoparticles is carried out in the environment of graphene oxide diluted with deionized water, by the electric arc method. The electric arc was applied at  200, 300, 400, and 500 volts with a three-second pulse duration of one minute. The results of ultraviolet-visible spectroscopy show that the resulting solution contains nanoparticles of graphene oxide and silver oxide.  Then, a CW 532 nm beam with a maximum power of 300 mW was used to determine the linear absorption of samples. Then, the z-scanning method was used to determine the nonlinear characteristics of the samples. After analyzing the graphs, the refraction and nonlinear absorption coefficients of each sample have been calculated. The results show that with increasing voltage, the concentration of nanoparticles produced in the samples increases and the linear absorption coefficient increases with it. The lowest value of linear absorbance is 1.31 (cm-1) and nonlinear absorbance is negative for all samples and its lowest value is 7.86 *10-3. Also, the nonlinear refractive index is negative for all the samples and its maximum value is 1. 61 *10-14. The thermo-optical coefficients of each of the samples have also been obtained.

Weyl semimetals show special quantum states of matter, which have nontrivial topological features and very interesting and unique applications in the spintronics industry. One method of making these materials is the use of alloying method. In this paper, the  alloys are constructed using the first-principles methods. After study of their stability, their structural, electronic, and topological properties have been studied. To study the structural and electronic properties of the alloys, the Wien2k package, based on density functional theory, has been used. Furthermore, the topological properties of the alloys have been calculated using the Wanniertools packages, based on the tight-binding method. Calculations show that the alloys, in the absence of spin-orbit coupling, have crossing points with fourfold degeneracy and band inversion. Therefore, they are topological Dirac semimetal. Considering the spin-orbit coupling, it is seen that alloys with concentrations of x = 0, 0.25, 0.5, 0.75 change to the normal semimetal by opening the band gap; but, the alloy with x = 1 concentration changes to the topological Weyl semimetal with 16 Weyl fermions couple. The full area of the first Brillouin zone (FBZ) was scanned to find the positions of the Weyl points. The results show that the Weyl points, with chirality of either +1 or -1, were scattered in the FBZ with the central symmetry, but all of them are far from the high-symmetry paths of FBZ. Furthermore, the surface state properties, like Fermi arcs, were calculated and studied for the NbSb Weyl semimetal using the Wanniertools computational packages.

Perovskite solar cells (PSCs) are advancing swiftly due to their remarkable increase in power conversion efficiency (PCE) compared to traditional photovoltaic technologies. The main purpose of this study is to investigate the efficiency of two distinct PSCS structures that use  as an inorganic perovskite active layer. The calculations are based on the optoelectronic model of the solar cell and the use of the finite element method to solve the continuity equations for current and charge density. Therefore, the layer thicknesses of different materials (as ETL and Active layer) are modified to find the better power conversion efficiency of these solar cells. The obtained results of simulation calculations illustrate that the first structure FTO/ITO/  /PEDOT: PSS/Au exhibits a maximum power conversion efficiency of 11.37%, with a short circuit current of 14.47 (mA/cm^2) and an open circuit voltage of 0.96 (V) and while the FTO/TiO2/ /Spiro- OMETAD/Au structure shows a maximum power conversion efficiency of 10.57%. The greatest power conversion efficiency for the aforementioned designs is 80 nm for the electron transporting layer is 80 nm and 200 nm for the inorganic active layer, respectively. The results of this article can be useful in the design of new-generation solar cells based on inorganic perovskite layers.