نشریه اپتوالکترونیک
سال ششم شماره 2 (پیاپی 15، زمستان 1402)

Laser-plasma accelerators are one of the new technologies to reach high energies. In this paper, while presenting the latest findings in the field of electron acceleration by laser pulse in a plasma channel, the mechanism of producing high-energy electrons in the interaction of femtosecond laser pulse with plasma is investigated and the amount of energy obtained in linear and non-linear interaction is estimated. Considering the density disturbances and the changes of the electric field of the wakefiled wave, it is shown that the energy of electrons decreases with the increase of plasma density and increases with the increase of plasma length and laser power. Also, the changes of the radius of the electron bubble and the number of accelerated electrons inside the bubble have been estimated at different plasma densities.

In this research, by using graphene nano-ribbons on silicon dioxide, a plasmonic channel with high confinement has been designed to guide surface plasmon polaritons. By adjusting the chemical potential of graphene, the transmission of the channel can be controlled. The simulation results show that by applying voltages of 1.5 and 8.3 V to graphene nano-ribbons, chemical potentials of 0.1 and 0.5 eV can be obtained and the channel loss can be changed from 88.23 to 0.91 dB/μm. Based on this, two logical zero and one states and switching operation can be realized. The figure-of-merit of 975.43 shows that there is a good ratio between the confinement of surface plasmons and their propagation loss. The coupling length of 99.1 μm shows that the power leakage to the adjacent channel can be controlled and the small size of the proposed decoder which is equal to 1.92 μm2 shows the importance of power leakage control. The contrast ratio of the decoder is 45.73 dB, which shows the ability of the device to distinguish logical levels of one and zero. Comparing the structure obtained from this research with other works confirms that the proposed design has been able to improve the performance of the optical decoder.

One of the fundamental issues in physics is measuring the refractive index of materials. Knowing the magnitude of the refractive index of a material plays a decisive role in predicting its behavior and the amount of light passing through it. There are different methods for measuring the refractive index. In this work, to measure the refractive index of thin samples, a system based on the optical deflectometry method has been designed and built. The theoretical basis of the work, the effective parameters and the measurement error of the system in measuring the refractive index of thin samples with a thickness of about a few millimeters have been investigated. After optimizing the system, the magnitude of the refractive index of YAG and quartz crystal samples was measured, which are widely used in various applications. Using three lasers of helium-cadmium (blue color, wavelength 442 nm), argon ion (green color, wavelength 514.5 nm) and helium-neon (red color, wavelength 632.8), dispersion of refractive index of these two substances were measured. The measured values for the refractive index in these three wavelengths were 1.44, 1.45, and 1.37 for the quartz sample and 1.81, 1.83, and 1.73 for the YAG crystal sample.

Structural and electronic properties of Iron oxide clusters (Fe2O3, Fe3O4, Fe4O6 and Fe6O9) and change this properties in bilayer graphene Due to placement of clusters between two layer of graphene have been investigated computationally using density functional theory (DFT). We find that By placing the studied clusters between two layers of graphene, graphene layers and clusters, which are initially neutral, are electrically charged, and their charges are equal in opposite sign. Also by placing the clusters between the two graphene layers, the resulting structures are magnetic, and total spin is equal to the cluster spin between the two graphene layers. so by placing Fe2O3, Fe3O4 and Fe4O6 clusters between two graphene layers, a chemical bond is formed between them and graphene layers, while the adsorption Fe6O9 cluster between two graphene layers is a physical adsorption.Keywords: Density Functional Theory, Bilayer Graphene, Iron Oxide clusters, Structural and Optical properties

This paper describes the interaction of three two-level atoms with a single-mode quantized field in the intensity-dependent coupling regime. Under a choice for the initial conditions for subsystems, where the atoms are prepared in the excited state and the cavity field is in the standard coherent state, the explicit form of the state vector of the whole system are obtained. To achieve this goal, the Laplace transform technique can be applied. By considering the intensity-dependent and constant coupling regimes, some of the most important physical properties of the system such as quantum entanglement between the atomic subsystem and the radiation field subsystem, atomic population inversion, quantum statistics of photons, and quadrature squeezing are numerically investigated. The numerical results show that the presence of nonlinear function can affect in the depth and the domain of the nonclassicality of the system. Also, by choosing different nonlinearity functions corresponding to any nonlinear oscillator with arbitrary nonlinear function, or corresponding to any solvable quantum system with a known discrete spectrum, the presented formalism would clearly be distinguished.

Health monitoring has always been one of the crucial challenges in medicine, and sensors have been widely used for this purpose. Meanwhile, optical sensors, especially those based on photonic crystal, have gained significant attention. For this purpose, the current research presents an optical sensor sample using a photonic crystal to monitor and detect four types of cancer cells. The proposed two-dimensional photonic crystal biosensor is made of silicon and is designed in an air substrate. However, it is designed by input and output waveguides and point resonators. After conducting simulations and analysis, the sensitivity of the proposed structure has been reported in the range of 500 nm/RIU with a quality factor of over 600. The simplicity and small size of the structure, which is in the micrometer range, make it suitable for biosensing applications in the medical field. It's important to note that numerical methods such as the finite difference time domain (FDTD) method were used to analyze the structure and obtain the output spectrum results, while the plane wave expansion (PWE) method was utilized to analyze the photonic band gap range of the of the primary photonic crystal structure.