Alireza Paknezhad
Abstract
Laser-plasma accelerators are considered one of the new technologies to reach high energies. In this paper, while reviewing recent 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 ...
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Laser-plasma accelerators are considered one of the new technologies to reach high energies. In this paper, while reviewing recent 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 increaseing plasma density and increases with the increasing of plasma length and laser power. Also, changes in radius of the electron bubble and the number of accelerated electrons inside the bubble have been estimated at different plasma densities
Mohammad Javad Maleki; Mohammad Soroosh; Gholamreza Akbarizadeh
Abstract
In this research, using graphene nano-ribbons on silicon dioxide, a plasmonic channel with high confinement has been designed for guiding surface plasmon polaritons. By adjusting the chemical potential of graphene, the channel's conductivity can be controlled. Simulation results show that by applying ...
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In this research, using graphene nano-ribbons on silicon dioxide, a plasmonic channel with high confinement has been designed for guiding surface plasmon polaritons. By adjusting the chemical potential of graphene, the channel's conductivity can be controlled. Simulation results show that by applying voltages of 1.5 and 8.3 volts to graphene nano-ribbons can obtained chemical potentials of 0.1 and 0.5 electron volts, and change the channel losses from 88.23 to 0.91 dB/μm. Accordingly, two logical states of zero and one and key 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 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 discrimination ratio of the decoder is 45.73 dB, demonstrating the ability of the device to distinguish logical levels of one and zero. Comparison of the structure obtained in this research with other works confirms that the proposed design has been able to improve the performance of the optical decoder.
Amirmohammad Beigzadeh; Mohammad Reza Rashidian Vaziri
Abstract
One of the fundamental issues in physics is measuring the refractive index of various 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 various methods for measuring the refractive ...
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One of the fundamental issues in physics is measuring the refractive index of various 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 various methods for measuring the refractive index. In this work, to measure the refractive index of thin samples, a system based on deflectometry method has been designed and built. The theoretical foundations of the work, effective parameters and system measurement errors in measuring the refractive index of thin samples with thickness of about a few millimeters have been investigated. After optimizing the system, the refractive index magnitude of YAG and quartz crystal samples were measured, both widely used in various scientific fields. 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 nm), optical dispersion of the refractive index of these two substances were measured at the radiation wavelengths of these lasers. The measured refractive index values at these 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.
Maryam Goudarzi; sara sadat parhizgar; javad Beheshtian
Abstract
In this article, the structural and electronic properties of Iron oxide clusters Fe2O3, Fe3O4, Fe4O6 and Fe6O9 ( which are among the most stable iron oxide clusters) and by placing these clusters between two layers of graphene and optimizing the resulting structure, change this properties in bilayer ...
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In this article, the structural and electronic properties of Iron oxide clusters Fe2O3, Fe3O4, Fe4O6 and Fe6O9 ( which are among the most stable iron oxide clusters) and by placing these clusters between two layers of graphene and optimizing the resulting structure, change this properties in bilayer graphene have been investigated computationally using density functional theory (DFT) have been investigated. The findings indicate that upon the placement of these clusters between two layers of graphene, graphene layers and clusters, initially neutral, become electrically charged, and their charges are equal but 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. By placing Fe2O3, Fe3O4 and Fe4O6 clusters between two graphene layers, a chemical bond forms between these clusters and graphene layers, whereas the adsorption of the Fe6O9 cluster between two graphene layers is a physical adsorption.
Keywords: Density Functional Theory, Bilayer Graphene, Iron Oxide clusters, Structural and Optical properties
Firouz Langarizadeh; Mohammad Javad Faghihi; Hamid Reza Baghshahi
Abstract
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 initial conditions for the subsystems, where the atoms are prepared in an excited state and the cavity field is in the standard coherent state, ...
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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 initial conditions for the subsystems, where the atoms are prepared in an excited state and the cavity field is in the standard coherent state, the explicit form of the total system's state vector is obtained. To achieve this goal, the Laplace transform technique is employed. 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 and the radiation field subsystem, atomic population inversion, quantum statistics of field 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 system's nonclassical behavior. Also, selecting 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.
Elham Bahmani; Jafar Emadi
Abstract
Health monitoring has always been one of the crucial challenges in the medical field, which is monitored by sensors. 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 ...
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Health monitoring has always been one of the crucial challenges in the medical field, which is monitored by sensors. 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 simulations and analysis, the sensitivity of the proposed structure has been reported within 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 is worth mentioning that numerical methods including the finite difference time domain (FDTD) method have been used for analyze the structure and obtain the output spectrum results, while the plane wave expansion (PWE) method has been utilized to analyze the photonic band gap range of the primary photonic crystal structure.