مجله فیزیک کاربردی
سال یازدهم شماره 3 (پیاپی 26، پاییز 1400)

Titanium dioxide (TiO2) is widely used in optical coating technology because of its stability and high index of refraction. The homogeneity of the chemical composition (stoichiometry) of the optical thin films plays an important role in the quality of the layers. Increasing the homogeneity increases the transmission coefficient and the laser-induced damage threshold and decreases the absorption coefficient. To increase the homogeneity of the layers, various methods are used during and after the process of film coating. Annealing (heating the deposited films up to a certain temperature) is a common technique. After the coating process, TiO2 thin film is uniformly heated to 400 °C to obtain the homogenization of the stoichiometry. In this research, the dependence of the homogeneity of the stoichiometry of TiO2 optical thin films on the rate of heat treatment (a gradual increase of heat treatment temperature over time) is investigated by X-ray Photoelectron Spectroscopy (XPS) of the samples. So, the 400 nm thick TiO2 layers are coated on the BK7 optical glass, utilizing an electron gun. Then, each sample is subjected to heat treatment at different rates. The data obtained from the XPS analysis show that the samples subjected to slow heat treatment (2.2 °C per minute, up to a final temperature of 400 °C) have a more homogeneous stoichiometry and contain higher amounts of TiO2. Based on the results, the laser-induced damage threshold of laser mirrors can be improved in the nanosecond and femtosecond regimes of radiation.

All-optical adders play a key role in the next generation of all-optical digital circuits. In this paper, using nonlinear resonance rings based on 2D photon crystals, a new structure has been designed to implement an all-optical half adder. To implement the required nonlinear ring resonators, some nonlinear defects made of doped glass were introduced between the core and outer layer of the resonant rings. The refractive index of nonlinear materials with high Kerr coefficients is very sensitive to the variation of optical intensity, so one can design optical switches by combining these materials with resonant rings. Two nonlinear resonant rings are used for designing the proposed all-optical half adder. Both rings are designed such that they can drop optical waves when the optical intensity is less than the switching threshold, but when the optical intensity is more than the switching threshold, they cannot drop the optical waves. The final structure has two input and two output ports. The proposed structure was simulated using Rsoft photonics CAD. According to the simulation results when both inputs ports are OFF, both output ports will remain OFF. If only one of the input ports is ON, the S port will be ON, and C will be OFF. Finally, when both input ports are ON, the C port will be ON, and S will be OFF. Therefore, these results prove that the proposed structure can work as an all-optical half adder. The maximum rise time for the proposed structure is about 1.5 ps.

In this paper, the behavior of the magnetic swimmers has been simulated in the presence of an external magnetic field. The studied system is formed of spherical self-propelled particles that have magnetic properties and are suspended in a box. We have applied a homogeneous magnetic field with circular symmetry. The particle-to-particle, particle-to-wall, and bipolar-bipolar interactions have been ignored. The motion of particles has been described by the Langevin equation, and the Fokker-Planck equation has been used for the expression of the evolution of the probability density distribution function. In the steady-state, solving these equations shows the collective behavior of these magnetic particles. In the absence of an external magnetic field, these particles are smoothly distributed in the box. The motion of particles has been controlled by an external magnetic field. Applying an externally homogeneous magnetic field, these particles are concentrated at boundaries. If the magnetic field is an exponential function of distance, particles will collect in the middle of the box. This type of research has applications in targeted drug delivery to damaged tissues and the separation of magnetic particles.

Surface plasmon resonance (SPR) is the excitation of cumulative charge oscillations in the metal-dielectric interface. Of the various surface plasmon-based measurement methods, phase-based measurement methods are the most accurate and sensitive. The wave phase can be measured with appropriate accuracy by various interferometry methods. The common path polarization heterodyne interferometry method compared to the conventional heterodyne method has the advantage of stability against changes in the ambient due to vibration and temperature changes. Increasing sensitivity has always been considered as one of the important challenges in designing and manufacturing various types of SPR-based sensors. In this study, after a theoretical investigation of enhancement of the phase sensitivity due to the addition of a quarter-wave plate in the common path polarization heterodyne interferometer, the SPR phase change in the standard common path polarization heterodyne interferometer arrangement is measured. Comparing the results with the results of the modified setup proves the phase sensitivity enhancement. Experimental results show a sensitivity enhancement of at least 3.5 times.

Persian Gulf (PG) is a shallow semi-enclosed sea that connects to the open ocean through the Strait of Hormuz. Thermocline occurs as a sharp decrease in temperature with depth in the subsurface layer as a result of water column classification in Persian Gulf on a seasonal basis. Impulses such as the northwest wind affect this process. In this paper, according to the results of Monte Michel research (1992) and the numerical study of Princeton ocean model (POM), with wind stress in both steady state and monthly average, the formation and development of summer thermocline in PG is investigated. The model results show that with the monthly variable wind, the thermocline develops as indicated by the summer observations. The formation of thermocline seems to decrease the dissolved oxygen in the water column due to lack of mixing as a result of induced stratification. The formation of thermocline seems to reduce the dissolved oxygen in the water column due to the lack of mixing, which is created as a result of water stratification. Also, the formation and development of thermocline as a fast temperature gradient in the water column affects the sound propagation used in offshore detection devices. According to the results of some sources of this research, The thermocline development happens more rapidly in Persian Gulf from spring to summer. Correlation coefficients of temperature and salinity between the model results and measurements were 0.85 and 0.80, respectively. In this paper, the research results obtained from the POM model are compared with the measurements. The rate of thermocline development was found to be between 0.1 to 0.2 meter per day in the Persian Gulf during the 6 months from winter to early summer

In this paper, thermal entanglement in four and five-qubit spin-star networks evolved by an XXX Hamiltonian model is studied. We examine the effect of temperature, magnetic field and coupling constant on the concurrence. We will show that the entanglement is decreased by increasing the temperature and the number of qubits. Also, we investigate quantum teleportation via a couple of spin-star networks in a thermal state. The average of fidelity as a function of temperature, magnetic field, and coupling constant is analyzed, too. It will be observed that as the temperature increases, the fidelity first decreases and then tends to a constant value. Moreover, with the increase of the external magnetic field, the average fidelity first increases and then gradually decreases, and in a certain amount of magnetic field, the average fidelity becomes zero. In addition, as the number of qubits increases, fidelity decreases with temperature. The results indicate that mean fidelity increases with increasing coupling constant.