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Plasma density ramp for relativistic self-focusing of an intense laser: Comment
, Article Journal of the Optical Society of America B: Optical Physics ; Volume 27, Issue 9 , 2010 , Pages 1731-1734 ; 07403224 (ISSN) ; Yazdani, E ; Habibi, M ; Lotfi, E ; Sharif University of Technology
Optical Society of American (OSA)
2010
Abstract
Gupta et al. [J. Opt. Soc. Am. B. 24, No. 5 (2007)] have introduced a localized upward plasma density ramp to overcome the defocusing of a laser beam. We report that there are fundamental mistakes in their work. First, the density profile formula that they have introduced is dimensionally incorrect. Second, the calculated dielectric constant is wrong as well, which renders their main spot size equation and the quantitative results unacceptable, and it seriously falters the results of the self-focusing. We correctly derived a new equation of the spot size, and the computational curves are also presented
Self-focusing up to the incident laser wavelength by an appropriate density ramp
, Article Laser and Particle Beams ; Volume 29, Issue 4 , 2011 , Pages 453-458 ; 02630346 (ISSN) ; Moshkelgosha, M ; Sharif University of Technology
Abstract
This work is devoted to improving relativistic self-focusing of intense laser beam in underdense unmagnetized plasma. New density profiles are introduced to achieve beam width parameter up to the wavelength of the propagating laser. By investigating variations of the beam width parameter in presence of different density profiles it is found that the beam width parameter is considerably decreased for the introduced density ramp comparing with uniform density and earlier introduced density ramp profiles. By using this new density profile high intensity laser pulses are guided over several Rayleigh lengths with extremely small beam width parameter
Production of Electron and Flat Ion Blocks by Using Ultra Intense Laser, Particularly in the Ultraviolet Range
, Ph.D. Dissertation Sharif University of Technology ; Anvari, Abbas (Supervisor) ; Sadighi Bonabi, Rasoul (Supervisor)
Abstract
In the present work, interaction of high power and ultra short laser pulse with plasma in both under relativistic and relativistic regimes is investigated. The accelerated ions and electron are studied. The effect of pulse laser shapes on generating of the optimum wakefield is studied to find the maximum generated wakefield amplitude. It is found that similar to the wakefield amplitude generated by single pulse, the wakefield amplitude produced by dual trailing depends on the pulse shape and their permutation. Furthermore, the interaction of sub-picosecond UV laser in sub-relativistic intensities with deuterium is investigated. At high plasma temperatures, based on the quantum correction in...
Self-Focusing of Laser Beam in Relativistic Quantum Plasma
, M.Sc. Thesis Sharif University of Technology ; Sadighi Bonabi, Rasoul (Supervisor)
Abstract
The phenomenon of relativistic self-focusing in nuclear fusion and laser-plasma interactions is very important. Under the influence of this phenomenon, the laser beam can move in plasma a few Rayleigh lengths and the interaction efficiency is improved. The relativistic self-focusing in inhomogeneous, homogeneous, collisional and collisionless plasmas has been studied in various conditions of plasma and laser in classical physics. In this thesis the propagation of a laser pulse at the X-ray wavelength range and its relativistic self-focusing in quantum plasma is investigated by numerical simulations. Initially, the interaction with a collisionless ramped density profile plasma target is...
Improving the relativistic self-focusing of intense laser beam in plasma using density transition
, Article Physics of Plasmas ; Volume 16, Issue 8 , 2009 ; 1070664X (ISSN) ; Habibi, M ; Yazdani, E ; Sharif University of Technology
2009
Abstract
The propagation of a Gaussian beam in underdense plasma with upward increasing density ramp is analyzed. In this work are shown that the spot size oscillations of laser beam increases and its amplitude shrinks with proper plasma density ramp. This causes the laser beam to become more focused and penetrations deep into the plasma by reduction of diffraction effect. The related focusing parameters are optimized to get the best possible focusing at the relativistic threshold intensity of Nd-glass laser and the effect of the laser intensity in the self-focusing parameters is also investigated. The analytical calculations are presented and showed more reliable results in comparison to the...
Generating the optimum self-focusing in the relativistic laser-plasma interaction
, Article IEEE Transactions on Plasma Science ; Volume 41, Issue 5 , 2013 , Pages 1570-1574 ; 00933813 (ISSN) ; Sadighi Bonabi, R ; Sharif University of Technology
2013
Abstract
In this paper, the effect of basic parameters of laser and plasma on controlling self-focusing is investigated, and based on the introduced effective parameter for self-focusing (EPSF), the effects of laser wavelength, the initial spot size of laser beam, the initial intensity of laser, and the plasma electron density on self-focusing are discussed. It is found that the relativistic self-focusing strongly depend on the laser wavelength and the beam intensity. The nonlinear effect of beam intensity on the introduced parameter EPSF indicates that after an increasing region for focusing, the self-focusing effect decreases at ultrarelativistic intensities. The effect of the initial beam spot...
Relativistic Gaussian laser beam self-focusing in collisional quantum plasmas
, Article Laser and Particle Beams ; Volume 33, Issue 3 , 2015 , Pages 397-403 ; 02630346 (ISSN) ; Rezaee, S ; Yazdani, E ; Anvari, A ; Sadighi Bonabi, R ; Sharif University of Technology
Cambridge University Press
2015
Abstract
Propagation of Gaussian X-ray laser beam is presented in collisional quantum plasma and the beam width oscillation is studied along the propagation direction. It is noticed that due to energy absorption in collisional plasma, the laser energy drops to an amount less than the critical value of the self-focusing effect and consequently, the laser beam defocuses. It is found that the oscillation amplitude of the laser spot size enhances while passing through collisional plasma. For the greater values of collision frequency, the beam width oscillates with higher amplitude and defocuses in a shallower plasma depth. Also, it is realized that in a dense plasma environment, the laser self-focusing...
Creation of twisted terahertz waves carrying orbital angular momentum via a plasma vortex
, Article Journal of Physics D: Applied Physics ; Volume 49, Issue 29 , 2016 ; 00223727 (ISSN) ; Rooholamininejad, H ; Bahrampour, A ; Sharif University of Technology
Institute of Physics Publishing
2016
Abstract
In this paper a new method for generating twisted terahertz radiation is proposed. The generation of twisted terahertz radiation in a plasma vortex, where the plasma density profile has helical structure, is investigated. The method is described on the basis of angular momentum exchange between plasma vortex and laser beam. The interaction of the vortex plasma and photons causes the laser angular momentum to change. Twisted terahertz radiation is produced at the beat frequency of laser and electron plasma waves. In this process, for Gaussian laser modes, the angular momentum of terahertz wave derives from the plasma vortex, while for the Laguerre-Gaussian it originates in the difference in...
Three-dimensional finite-difference time-domain analysis of gas ionization
, Article 2008 International Symposium on Telecommunications, IST 2008, Tehran, 27 August 2008 through 28 August 2008 ; October , 2008 , Pages 157-162 ; 9781424427512 (ISBN) ; Shishegar, A. A ; Sharif University of Technology
2008
Abstract
The propagation of intense optical beams in a gas undergoing ionization is analyzed through a threedimensional finite-difference time-domain (3D-FDTD) scheme. The propagation dynamics include the effects of diffraction, nonlinear self-focusing, and ionization. For sufficiently intense optical beams the neutral gas undergoes ionization, generating a plasma which tends to defocus the beam. Balancing of diffraction, plasma defocusing, and nonlinear self-focusing may lead to self-guided results. In this paper, necessary relations have been introduced into the conventional FDTD formulation to account for the nonlinear behaviors. Furthermore, a concurrent utilization of computer memory and disk...
Investigation of Energetic Electrons Behavior in Ultrafast High Power Laser-Matter Interaction
, Ph.D. Dissertation Sharif University of Technology ; Sadighi-Bonabi, Rasoul (Supervisor)
Abstract
Resent advances in ultra-intense short-pulse lasers and their numerous applications stimulated the research activities in important fields such as generation of high-energy electron and ion beams, monoenergetic electron beam, monoenergetic ion beam, X-ray emission, terahertz radiation, high harmonic and attosecond pulses generation. In all above mentioned applications the relativistic electrons behavior especially the electron density distribution and the velocity of electrons play an important role.
Investigating the behavior of relativistic electrons which are generated in the interaction of high power femtosecond lasers with plasma and their related applications is the main purpose...
Investigating the behavior of relativistic electrons which are generated in the interaction of high power femtosecond lasers with plasma and their related applications is the main purpose...
Three-dimensional finite-difference time-domain analysis of nonlinear self-focusing in air
, Article 2008 International Symposium on Telecommunications, IST 2008, Tehran, 27 August 2008 through 28 August 2008 ; October , 2008 , Pages 163-168 ; 9781424427512 (ISBN) ; Shishegar, A. A ; Sharif University of Technology
2008
Abstract
Through using a three-dimensional finitedifference time-domain (3D-FDTD) scheme, we analyze nonlinear self-focusing in air as a Kerr medium. For sufficiently intense laser beams, the gaseous medium can behave as a strong positive lens which tends to focus the beam. Our simulations' major focus is on the propagation characteristics of an intense continuous-wave laser beam. Necessary relations have been introduced into the conventional FDTD formulation to account for the nonlinear behavior of air. The results clearly indicate that sufficient amounts of optical intensity may lead to self-focusing immediately in front of the laser aperture. ©2008 IEEE
Resonant second harmonic generation in plasma by self-focused twisted beam
, Article Optics Communications ; Volume 341 , April , 2015 , Pages 295-301 ; 00304018 (ISSN) ; Sohailya, S ; Bahrampour, A ; Sharif University of Technology
Elsevier
2015
Abstract
The resonant second harmonic generation in the presence of a wiggler magnetic field by twisted laser plasma interaction is surveyed. The wiggler magnetic field provides additional momentum required for the phase matching. The Laguerre-Gaussian modes can be used to control the self-focusing and improve the second harmonic generation in laser plasma interaction. The wave equations for the fundamental and the second harmonic fields have been solved in the paraxial approximation. The generation of the second harmonic considering self-focusing is investigated. Also, the dependence of the second harmonic power on the propagation distance for different values of initial fundamental beam intensity,...
Nonlinear interaction of intense hypergeometric Gaussian subfamily laser beams in plasma
, Article Optics and Laser Technology ; Volume 81 , 2016 , Pages 40-45 ; 00303992 (ISSN) ; Vaziri, M. (Khamedi) ; Rooholamininejad, H ; Bahrampour, A. R ; Sharif University of Technology
Elsevier Ltd
Abstract
Propagation of Hypergeometric-Gaussian laser beam in a nonlinear plasma medium is investigated by considering the Source Dependent Expansion method. A subfamily of Hypergeometric-Gaussian beams with a non-negative, even and integer radial index, can be expressed as the linear superposition of finite number of Laguerre-Gaussian functions. Propagation of Hypergeometric-Gaussian beams in a nonlinear plasma medium depends on the value of radial index. The bright rings' number of these beams is changed during the propagation in plasma medium. The effect of beam vortex charge number l and initial (input) beam intensity on the self-focusing of Hypergeometric-Gaussian beams is explored. Also, by...
Layers from initial Rayleigh density profiles by directed nonlinear force driven plasma blocks for alternative fast ignition
, Article Laser and Particle Beams ; Volume 27, Issue 1 , 2009 , Pages 149-156 ; 02630346 (ISSN) ; Cang, Y ; Sadighi Bonabi, R ; Hora, H ; Osman, F ; Sharif University of Technology
2009
Abstract
Measurement of extremely new phenomena during the interaction of laser pulses with terawatt and higher power and picoseconds with plasmas arrived at drastically different anomalies in contrast to the usual observations if the laser pulses were very clean with a contrast ratio higher than 108. This was guaranteed by the suppression of prepulses during less than dozens of ps before the arrival of the main pulse resulting in the suppression of relativistic self-focusing. This anomaly was confirmed in many experimental details, and explained and numerically reproduced as a nonlinear force acceleration of skin layers generating quasi-neutral plasma blocks with ion current densities above 1011...