Showing 6 results for Bani
A. S. Arabanian, A. Manteghi, F. Fereidouni, R. Massudi,
Volume 2, Issue 1 (International Journal of Optics and Photonics (IJOP) Vol. 2, No. 1, Winter 2008)
Abstract
Time resolved laser induced incandescence (LII) technique is used to measure size distribution of soot nanoparticles of candle's flame. Pulsed Nd:YAG laser is used to heat nanoparticles to incandescence temperature and the resulting signal is measured. Mass and energy balance equations are numerically solved to calculate temperature of soot particles in low fluence regime. Assuming Plank black body radiation and lognormal size distribution for soot particles, the intensity of LII signals are calculated. Using Levenberg-Marquart nonlinear regression algorithm and numerical and experimental LII signals, mean particle size and distribution width of soot nanoparticles are obtained.
Ali Mohammadi, Atoosa Sadat Arabanian, Ali Dalafi,
Volume 12, Issue 2 (International Journal of Optics and Photonics (IJOP) Vol 12, No 2, Summer-Fall 2018)
Abstract
In this paper, we have investigated the dependence of the spectral entanglement and indistinguishability of photon pairs produced by the spontaneous parametric down-conversion (SPDC) procedure on the bandwidth of spectral filters used in the detection setup. The SPDC is a three-wave mixing process which occurs in a nonlinear crystal and generates entangled photon pairs and utilizes as one of the most useful resources in a variety of fields such as quantum computation, quantum cryptography, and quantum communication. The amount of the spectral entanglement and the indistinguishability of photon pairs are the two critical characteristics of the photon pairs determining their potential applications. The degree of the spectral entanglement of a quantum system, i.e. photon pairs, is determined by the entanglement entropy which is a measure of the system disorder. First, we derive the eigenvalue equation of reduced density operator of the signal and the idler photons in terms of the bandwidth of spectral filters. Then, by numerically solving the eigenvalue equation, we calculate the Schmidt coefficients for different values of the bandwidth of spectral filters. Finally, by calculating the entropy operator one can obtain the dependence of spectral entanglement of the photon pairs on filter bandwidth. The amount of indistinguishability of the photon pairs is measured by the visibility of the HOM diagram. Since the whole spectral information of the photon pairs exists in their two-photon mode function, using this function and the presented model we calculate the amount of indistinguishability by obtaining the visibility of the HOM diagram for different values of the bandwidth of the spectral filters. In this way, the dependence of the indistinguishability of the photon pairs on this quantity is reported.
Samaneh Biabani, Gholamreza Foroutan,
Volume 13, Issue 2 (International Journal of Optics and Photonics (IJOP) Vol 13, No 2, Summer-Fall 2019)
Abstract
The dynamics of fast gas heating in a high power microwave discharge in air, is investigated in the framework of FDTD simulations of the Maxwell equations coupled with the fluid simulations of the plasma. It is shown that, an ultra-fast gas heating of the order of several 100 Kelvins occurs in less than 100 ns. The main role in the heating is played by the electron impact dissociation of , dissociation via quenching of metastable states of , as well as, quenching by nitrogen molecules. Among the electronically excited metastable states, are the most important species. Slow heating of the gas above 1 is attributed to the vibrational relaxation processes of , among them vibrational-translational relaxation of demonstrates the highest heating rate. The heating rate and thus the gas temperature are significantly increased with increasing of the microwave pulse amplitude, pulse width, and the gas pressure. In all cases, enhanced dissociation is the main factor behind the enhanced gas heating. The same effects are observed for increasing of the initial gas temperature, and percentage in a mixture.
Hamid Haghmoradi, Atoosa Sadat Arabanian, Reza Massudi,
Volume 14, Issue 1 (Winter-Spring 2020)
Abstract
In this paper, design and fabrication of an internal resonant enhanced frequency doubling of the continuous-wave ytterbium-doped fiber laser at 1064nm using a Fabry-Perot bow tie cavity inside the fiber laser cavity is presented. The 3.5W power coupled into the enhancement cavity is amplified to 163W by the intracavity passive locking technique. By placing an LBO crystal within this resonant enhancement cavity, conversion efficiency of the second harmonic generation of the laser in continuous regime is increased from 0.023% to 51.42% (i.e. about 2200 times) which results to generation of 1.8W light at 532nm.
Mohammad Amin Bani, Majid Nazeri, Ahmad Sajedi Bidgoli,
Volume 15, Issue 2 (Summer-Fall 2021)
Abstract
In this paper, the frequency response of a detector antenna is investigated when a layer of dielectric is placed on it. For this purpose, the surface wave theory has been used to explain the propagation of the current pulses in the antenna electrodes. Examinations are also performed of the propagation spectra of two types of terahertz antennas, bow-tie and dipole (with LT-GaAs substrates), on which the dielectrics of gallium arsenide and silica are located. These antennas are simulated through the CST software (FDTD method). The simulations show that the presence of a surrounding dielectric on the surface of an antenna affects the velocity of the current pulse propagation on the electrodes. It is also shown that the change in the thickness and position of the surrounding dielectric have a negative effect on quality of detector antenna by shift its spectral response to lower frequencies.
Nastaran Kahrarian, Atoosa Sadat Arabanian, Zinab Moradi Alvand, Hasan Rafati, Reza Massudi,
Volume 18, Issue 1 (10-2024)
Abstract
The modification of cell surface structures has become a focal point in cell biology, with methods like drugs, chemicals, and non-destructive techniques such as laser light exposure being utilized. In particular, exposure to femtosecond laser pulses has been found to increase cell permeability to formulations without causing thermal damage. This study aimed to observe and document the changes in the structure of Staphylococcus aureus bacteria when they were optically trapped and subjected to femtosecond laser pulses, along with the application of a medicinal substance, over 20 minutes. The research successfully determined the optimal power and exposure time of the laser light on the bacterial surface and demonstrated the ability of femtosecond laser pulses to enhance the efficacy of the medicinal substance.
