Numerical simulation of performance of AlGaN/GaN terahertz quantum cascade laser
Ali Asghar
Khorami
پژوهشکده فیزیک کاربردی وستارهشناسی، دانشگاه تبریز
author
Asghar
Asgari
پژوهشکده فیزیک کاربردی وستارهشناسی، دانشگاه تبریز
author
text
article
2013
per
In this paper, we present numerical calculation to study the effect of temperature on lifetime of laser levels, optical gain and output power in an unintentionally doped AlGaN/GaN quantum cascade laser. In the calculations, we have included the effects of internal polarization fields, and different scattering mechanisms using self-consistent numerical calculation of Schrödinger, Poisson and laser rate equations. The analysis of our results clearly indicates that the III- nitride based quantum well cascade lasers are one of the best coherent sources for the generation of the terahertz waves. Also, the threshold current density, the optical gain and output power were analyzed at different temperatures. A comparison of our results with the experimental data has shown good agreement.
Journal of Research on Many-body Systems
Regional Information Center for Science and Technology (RICeST)
2322-231X
2
v.
4
no.
2013
1
10
http://jrmbs.scu.ac.ir/article_10517_18d929c819f781e055ffa3438ec25fd5.pdf
Ab-initio study of potassium doping effects on electronic and crystallographic structure of superconductor YBa2-xKXCu3O7
Mahnaz
Mohammadi
دانشکده فیزیک، دانشگاه کاشان
author
Bahram
Khoshnevisan
دانشکده فیزیک، دانشگاه کاشان
author
text
article
2013
per
DFT ab-initio calculation (using plane waves and pseudo-potential approach) has been employed for a systematic study of potassium substitution in YBa2-xKxCu3O7 samples. The electronic structure, energy levels and the density of states (DOS) with different potassium doping amounts (x=0.16, 0.25, 0.5, 0.75) were calculated under the generalized gradient approximation (GGA). The substitution of potassium changes the electronic band structure and DOS. These modifications are responsible for empirical reports of decreasing the TC with increasing of the potassium. In addition, our results about the variation of lattice parameters (a, b and c) of the system are in good agreement with experimental reports according to the Rietveld refinement of XRD data.
Journal of Research on Many-body Systems
Regional Information Center for Science and Technology (RICeST)
2322-231X
2
v.
4
no.
2013
11
20
http://jrmbs.scu.ac.ir/article_10518_3a60f63e60f8af51b1181881b31fb4dc.pdf
A study of longitudinal development of secondary particles, produced in the atmosphere due to the extensive air shower of high energy cosmic rays
Saeed
Doostmohammadi
دانشکده فیزیک دانشگاه شهید باهنر کرمان
author
Jalileddin
Fatemi
دانشکده فیزیک دانشگاه شهید باهنر کرمان
author
Hamideh
Mahmoudimeymand
دانشکده فیزیک دانشگاه شهید باهنر کرمان
author
text
article
2013
per
Ultra-high energy cosmic rays (with energies above 1014 eV), by interaction with the atmosphere, generate cascades of particles (secondary particles) which increase in the atmosphere, depending on the level of penetration. Then they reach a maximum content. Following this stage, their numbers are decrease until they arrive at the surface detectors. In this paper, by using Yakutsk, Volcano Ranch and Haverah Park array data, where there are in the different altitudes, the amount of variation of secondary particles is discussed.
Journal of Research on Many-body Systems
Regional Information Center for Science and Technology (RICeST)
2322-231X
2
v.
4
no.
2013
21
26
http://jrmbs.scu.ac.ir/article_10519_10699675e1c0c28845fced61fabc060b.pdf
Investigation of Hubbard parameter on structural, magnetic and electronic properties of mono ferrite strontium
Hamdollah
Salehi
گروه فیزیک، دانشکده علوم، دانشگاه شهید چمران
author
Zohreh
Javdani
گروه فیزیک، دانشکده علوم، دانشگاه شهید چمران
author
Hojat Allah
Badehian
گروه فیزیک، دانشکده علوم، دانشگاه شهید چمران
author
text
article
2013
per
In this work, the effect of Hubbard parameter on structural, magnetic and electronic properties of SrFe2O4 has been investigated. The calculations have been performed by Full-Potential-Linearized Augmented Plane Wave (FP-LAPW) method in the framework of density functional theory with different approximations about exchange-correlations energy by WIEN2k package. The results indicated that for SrFe2O4, ferrimagnetic is the most stable state and there are six different spin configurations for ferromagnetic. "Generalized Gradient" and "Local Spin Density" Approximations were not appropriate for explaining the expected band gap and magnetic moment of the compound. Therefore, other approximations like GGA+U were used. Band gap and lattice constants improved by using this approximation. In Hubbard approximation, band gap and magnetic moment were calculated per different U parameters and U=4.5 eV was chosen for future calculations. The effect of pressure on the band gap was calculated and it was found that by increasing pressure, band gap for both spin up and down states increases. Lattice constants results are in consistent with experimental studies. However, the amount for bulk modulus, magnetic moment and band gap have not been reported experimentally.
Journal of Research on Many-body Systems
Regional Information Center for Science and Technology (RICeST)
2322-231X
2
v.
4
no.
2013
27
36
http://jrmbs.scu.ac.ir/article_10520_7512d1db656323217017b57bf882ef8c.pdf
Electromagnetic wave transmission through inhomogeneous over-dense plasma
Seddigheh
Miraboutalebi
گروه فیزیک، دانشکده علوم پایه، دانشگاه آزاد اسلامی واحد تهران شمال
author
Mohammad Kazem
Khadivi Borogeni
گروه فیزیک، دانشگاه پیام نور، مرکز شیراز
author
Leyla
Rajaei
دانشکده فیزیک، دانشگاه قم
author
text
article
2013
per
Here, the transmission of electromagnetic waves was studied through an inhomogeneous over-dense plasma medium in the presence of a magnetic field. This plasma medium is in fact a kind of left handed material (LHM), in which the excitation of the surface waves is the principle actor for the transmission of electromagnetic waves. A specific structure was introduced for the overdense plasma and results showed that the surface waves can effectively be excited on both sides of the structure. The charge density of the plasma layer is supposed to have spatial variation, and in such a way that the density gradually (linearly) increases from both sides of the slab. In this way, the generalized electric permittivity of the plasma structure linearly acquires negative values and then, with the same rate, becomes positive. It is only considered the normal mode of the system. The amplitude of the electromagnetic waves was studied for the total structure, in the normal mode, for the perpendicular and oblique incidences. It was found that in this mode the surface waves can be excited effectively at the plasma surface, and hence the introduced structure has the capability of being used as a super lens.
Journal of Research on Many-body Systems
Regional Information Center for Science and Technology (RICeST)
2322-231X
2
v.
4
no.
2013
37
46
http://jrmbs.scu.ac.ir/article_10521_71f60c57858235d19a2493bb75aa79d4.pdf
Level statistics of stable and radioactive nuclei by using kernel density estimation method
Bahram
Rashidian Maleki
دانشکده فیزیک، گروه فیزیک هسته¬ای، دانشگاه تبریز
author
Hadi
Sabri
دانشکده فیزیک، گروه فیزیک هسته¬ای، دانشگاه تبریز
author
Mohammad Ali
Jafarizadeh
دانشکده فیزیک، گروه فیزیک هسته¬ای، دانشگاه تبریز
author
text
article
2013
per
Using experimental data, the Nearest Neighbor Spacing Distribution (NNSD) function for both stable and radioactive nuclei was directly calculated by kernel density estimation (KDE) method and the distance between the obtained function and regular and chaotic limits was determined using Kullback-Leibeller Divergence (KLD) method. The results show that stable nuclei have more regular spectra than radioactive nuclei and nuclei with alpha decay have more irregular spectra than other nuclei. This indicates that stable nuclei have a more symmetrical structure than radioactive nuclei.
Journal of Research on Many-body Systems
Regional Information Center for Science and Technology (RICeST)
2322-231X
2
v.
4
no.
2013
47
54
http://jrmbs.scu.ac.ir/article_10522_fcf2dc5c5aa2985c82db36b5f6b83106.pdf