scholarly journals Dynamics of Gaussian spikes on Gaussian laser beam in relativistic plasma

2009 ◽  
Vol 27 (4) ◽  
pp. 587-593 ◽  
Author(s):  
A. Singh ◽  
M. Aggarwal ◽  
T.S. Gill
Keyword(s):  
Differential Equations ◽  
Laser Beam ◽  
Nonlinear Differential Equations ◽  
Beam Width ◽  
Main Beam ◽  
Gaussian Laser Beam ◽  
Runge Kutta Method ◽  
Self Focusing ◽  
Gaussian Perturbation ◽  
Paraxial Ray

AbstractIn the present paper, we have investigated the growth of a Gaussian perturbation superimposed on a Gaussian laser beam. The nonlinearity we have considered is of relativistic type. We have setup the nonlinear differential equations for beam width parameter of the main beam, growth and width of the laser spike by using the WKB and paraxial ray approximation. These are coupled ordinary differential equations and therefore these are simultaneously solved numerically using the Runge Kutta method. It has been observed from the analysis that self-focusing/defocusing of the main beam and the spike determine the growth dynamic of the spike.

scholarly journals Growth of spike in relativistic Gaussian laser beam in a plasma and its effect on third-harmonic generation

2017 ◽  
Vol 35 (1) ◽  
pp. 137-144 ◽  
Author(s):  
N. Ahmad ◽  
S. T. Mahmoud ◽  
G. Purohit
Keyword(s):  
Laser Beam ◽  
Beam Width ◽  
Spot Size ◽  
Main Beam ◽  
Gaussian Laser Beam ◽  
Third Harmonic ◽  
Single Beam ◽  
Self Focusing ◽  
Diffraction Divergence ◽  
Paraxial Ray

AbstractA paraxial ray formalism is developed to study the evolution of an on axis intensity spike on a Gaussian laser beam in a plasma dominated by relativistic and ponderomotive non-linearities. Ion motion is taken to be frozen. A single beam width parameter characterizes the evolution of the spike. The spike introduces two competing influences: diffraction divergence and self-convergence. The former grows with the reduction in spot size of the spike, while the latter depends on the gradient in non-linear permittivity. Parameter δ = (ωpr00/c) a00/(3.5 r00/r01) characterizes the relative importance of the two, where r01 and r00 are the spike and main beam radii, ωp is the plasma frequency, and a00 is the normalized laser amplitude. For δ > 1, the intensity ripple causes faster self-focusing of the beam; higher the ripple amplitude stronger the focusing. In the opposite limit, diffraction divergence increases more rapidly, slowing down the self-focusing of the beam. As the beam intensity rises due to self-focusing, it causes stronger generation of the third harmonic.

Relativistic self-focusing of a rippled laser beam in a plasma

1999 ◽  
Vol 62 (4) ◽  
pp. 389-396 ◽  
Author(s):  
M. V. ASTHANA ◽  
A. GIULIETTI ◽  
DINESH VARSHNEY ◽  
M. S. SODHA
Keyword(s):  
Refractive Index ◽  
Laser Beam ◽  
The Self ◽  
Laser Beams ◽  
Radial Dependence ◽  
Main Beam ◽  
Gaussian Laser Beam ◽  
Self Focusing ◽  
Saturation Effects ◽  
Paraxial Ray

This paper presents an analysis of the relativistic self-focusing of a rippled Gaussian laser beam in a plasma. Considering the nonlinearity as arising owing to relativistic variation of mass, and following the WKB and paraxial-ray approximations, the phenomenon of self-focusing of rippled laser beams is studied for arbitrary magnitude of nonlinearity. Pandey et al. [Phys. Fluids82, 1221 (1990)] have shown that a small ripple on the axis of the main beam grows very rapidly with distance of propagation as compared with the self-focusing of the main beam. Based on this analogy, we have analysed relativistic self-focusing of rippled beams in plasmas. The relativistic intensities with saturation effects of nonlinearity allow the nonlinear refractive index in the paraxial regime to have a slower radial dependence, and thus the ripple extracts relatively less energy from its neighbourhood.

scholarly journals Relativistic ponderomotive self-focusing of quadruple Gaussian laser beam in cold quantum plasma

2018 ◽  
Vol 36 (3) ◽  
pp. 353-358 ◽  
Author(s):  
Richa ◽  
Munish Aggarwal ◽  
Harish Kumar ◽  
Ranju Mahajan ◽  
Navdeep Singh Arora ◽  
...  
Keyword(s):  
Refractive Index ◽  
Laser Beam ◽  
Electron Temperature ◽  
Density Perturbation ◽  
Beam Width ◽  
Quantum Plasma ◽  
Gaussian Laser Beam ◽  
Self Focusing ◽  
Linear Differential ◽  
Paraxial Ray

AbstractIn the present paper, we have investigated self-focusing of the quadruple Gaussian laser beam in underdense cold quantum plasma. The non-linearity chosen is associated with the relativistic mass effect that arises due to quiver motion of electron and electron density perturbation caused by ponderomotive force. The non-linearity modifies the plasma frequency in the dielectric function and hence the refractive index of the medium. The focusing/defocusing of the quadruple laser depends on the refractive index of the medium. We have set up non-linear differential equation that controls the beam width parameter by using well-known paraxial ray approximation and Wentzel–Krammers–Brillouin approximation. The effect of intensity parameter and electron temperature is observed on laser beam self-focusing in the presence of cold quantum plasma. From the results, it is revealed that electron temperature and the initial intensity of the laser beam control the profile dynamics of the laser beam.

scholarly journals Combined effect of relativistic and ponderomotive nonlinearity on self-focusing of Gaussian laser beam in a cold quantum plasma

2016 ◽  
Vol 34 (3) ◽  
pp. 426-432 ◽  
Author(s):  
H. Kumar ◽  
M. Aggarwal ◽  
Richa ◽  
T.S. Gill
Keyword(s):  
Laser Beam ◽  
Beam Width ◽  
Combined Effect ◽  
Quantum Plasma ◽  
Gaussian Laser Beam ◽  
Relativistic Case ◽  
Self Focusing ◽  
Ponderomotive Nonlinearity ◽  
Paraxial Ray ◽  
The Impact

AbstractIn the present paper, we have investigated self-focusing of Gaussian laser beam in relativistic ponderomotive (RP) cold quantum plasma. When de Broglie wavelength of charged particles is greater than or equal to the inter particle distance or equivalently the temperature is less than or equal to the Fermi temperature, quantum nature of the plasma constituents cannot be ignored. In this context, we have reported self-focusing on account of nonlinear dielectric contribution of RP plasma by taking into consideration the impact of quantum effects. We have setup the nonlinear differential equation for the beam-width parameter by paraxial ray and Wentzel Kramers Brillouin approximation and solved it numerically by the Runge Kutta Fourth order method. Our results show that additional self-focusing is achieved in case of RP cold quantum plasma than relativistic cold quantum plasma and classical relativistic case. The pinching effect offered by quantum plasma and the combined effect of relativistic and ponderomotive nonlinearity greatly enhances laser propagation up to 20 Rayleigh lengths.

scholarly journals Relativistic interaction of rippled laser beams with plasmas

2000 ◽  
Vol 18 (3) ◽  
pp. 399-403 ◽  
Author(s):  
M.V. ASTHANA ◽  
A. GIULIETTI ◽  
D. GIULIETTI ◽  
L.A. GIZZI ◽  
M.S. SODHA
Keyword(s):  
Laser Beam ◽  
Critical Power ◽  
Radial Dependence ◽  
Main Beam ◽  
Gaussian Laser Beam ◽  
Self Focusing ◽  
Relativistic Interaction ◽  
Saturation Effects ◽  
Paraxial Ray ◽  
Initial Power

An investigation of the growth of a radially symmetrical ripple, superimposed on a Gaussian laser beam in a plasma is presented. Based on WKB and paraxial ray approximation the phenomenon of relativistic self-focusing (RSF) is analytically investigated. The differential equation for beamwidth parameter of rippled laser beam is evaluated. The ripple gets focused when the initial power of the ripple is greater than the critical power for focusing. The focusing is found to be considerably affected by the power of the main beam and the phase angle between the electric vectors of the main beam and the ripple. At higher intensities the saturation effects of nonlinearity become predominant, making the nonlinear refractive index in the paraxial region have slower radial dependence, and thus the ripple extract relatively less energy from its neighborhood. The case of magnetized plasmas is also preliminarily discussed.

scholarly journals Significant enhancement in the propagation of cosh-Gaussian laser beam in a relativistic–ponderomotive plasma using ramp density profile

2018 ◽  
Vol 36 (2) ◽  
pp. 179-185 ◽  
Author(s):  
Harish Kumar ◽  
Munish Aggarwal ◽  
Richa ◽  
Dinkar Sharma ◽  
Sumit Chandok ◽  
...  
Keyword(s):  
Laser Beam ◽  
Gaussian Beam ◽  
Beam Width ◽  
Beam Radius ◽  
Gaussian Laser Beam ◽  
Focusing Effect ◽  
Runge Kutta Method ◽  
Linear Differential ◽  
Paraxial Ray ◽  
Selection Of

AbstractThe paper presents an investigation on self-focusing of cosh-Gaussian (ChG) laser beam in a relativistic–ponderomotive non-uniform plasma. It is observed numerically that the selection of decentered parameter and initial beam radius determines the focusing/defocusing of ChG laser beam. For given value of these parameters, the plasma density ramp of suitable length can avoid defocusing and enhance focusing effect significantly. Focusing length and extent of focusing may also be controlled by varying slope of the ramp density. A comparison with Gaussian beam has also been attempted for optimized set of parameters. The results establish that ChG beam focuses earlier and sharper relative to Gaussian beam. We have setup the non-linear differential equation for the beam width parameter using Wentzel–Kramers–Brillouin and paraxial ray approximation and solved it numerically using Runge–Kutta method.

scholarly journals Effect of self-focused cosh Gaussian laser beam on the excitation of electron plasma wave and particle acceleration

2016 ◽  
Vol 34 (4) ◽  
pp. 621-630 ◽  
Author(s):  
B. Gaur ◽  
P. Rawat ◽  
G. Purohit
Keyword(s):  
Particle Acceleration ◽  
Laser Beam ◽  
Plasma Wave ◽  
Electron Plasma ◽  
The Self ◽  
Acceleration Process ◽  
Gaussian Laser Beam ◽  
Electron Plasma Wave ◽  
Self Focusing ◽  
Paraxial Ray

AbstractThis work presents an investigation of the self-focusing of a high-power laser beam having cosh Gaussian intensity profile in a collissionless plasma under weak relativistic-ponderomotove (RP) and only relativistic regimes and its effect on the excitation of electron plasma wave (EPW), and particle acceleration process. Nonlinear differential equations have been set up for the beam width and intensity of cosh Gaussian laser beam (CGLB) and EPW using the Wentzel-Kramers-Brillouin and paraxial-ray approximations as well as fluid equations. The numerical results are presented for different values of decentered parameter ‘b’ and intensity parameter ‘a’ of CGLB. Strong self-focusing is observed in RP regime as compared with only relativistic nonlinearity. Numerical analysis shows that these parameters play crucial role on the self-focusing of the CGLB and the excitation of EPW. It is also found that the intensity/amplitude of EPW increases with b and a. Further, nonlinear coupling between the CGLB and EPW leads to the acceleration of electrons. The intensity of EPW and energy gain by electrons is significantly affected by including the ponderomotive nonlinearity. The energy of the accelerated electrons is increased by increasing the value of ‘b’. The results are presented for typical laser and plasma parameters.

scholarly journals Weakly relativistic self-focusing of Gaussian laser beam in magnetized cold quantum plasma

2017 ◽  
Vol 35 (4) ◽  
pp. 699-705 ◽  
Author(s):  
M. Aggarwal ◽  
V. Goyal ◽  
Richa ◽  
H. Kumar ◽  
T.S. Gill
Keyword(s):  
Magnetic Field ◽  
Laser Beam ◽  
Interparticle Distance ◽  
Beam Propagation ◽  
Magnetized Plasma ◽  
Quantum Plasma ◽  
Computational Technique ◽  
Gaussian Laser Beam ◽  
Self Focusing ◽  
Paraxial Ray

AbstractIn the present paper, we have studied self-focusing of Gaussian laser beam in weakly relativistic magnetized cold quantum plasma. When interparticle distance is comparable to the de Broglie wavelength of charged particles, we cannot neglect the quantum contribution of plasma constituents. Therefore, propagation characteristics are studied by taking in to account quantum contribution in the presence of static magnetic field applied along the beam propagation. Our results show that the magnetic field plays a key role in achieving additional focusing, it modifies the quiver motion of electrons by adding cyclotron frequency to the natural frequency of oscillating electrons during laser beam propagation. The results are compared with those of weakly relativistic quantum plasma and weakly relativistic magnetized plasma. The self-focusing is found to be more pronounced when axial magnetic field is increased in the present model. We have setup the non-linear differential equation for the evolution of beam-width parameter by well-known paraxial ray approximation and solved it with the help of computational technique.

scholarly journals Relativistic self-focusing and self-phase modulation of cosh-Gaussian laser beam in magnetoplasma

2011 ◽  
Vol 29 (2) ◽  
pp. 183-191 ◽  
Author(s):  
Tarsem Singh Gill ◽  
Ravinder Kaur ◽  
Ranju Mahajan
Keyword(s):  
Magnetic Field ◽  
Laser Beam ◽  
Field Distribution ◽  
Phase Modulation ◽  
Variational Approach ◽  
Beam Width ◽  
Propagation Characteristics ◽  
Gaussian Laser Beam ◽  
Self Phase Modulation ◽  
Self Focusing

AbstractIn this paper, we have investigated the propagation characteristics of cosh-Gaussian laser beam in magnetoplasma using relativistic nonlinearity. The field distribution in the medium is expressed in terms of beam width parameter an and decentred parameter b. An appropriate nonlinear Schräodinger equation has been solved analytically using variational approach. The behaviour of beam width parameter with dimensionless distance of propagation ξ for various b values is examined. Self-phase modulation and self-trapping is also studied under variety of parameters. Further, the effect of magnetic field on self-focusing of the beam have been explored.

scholarly journals Direct Electron Acceleration By An Intense Nonparaxial Cosh-Gaussian Laser Beam Driven Electron Plasma Wave in Plasma

2021 ◽  
Author(s):  
Gunjan Purohit ◽  
Bineet Gaur ◽  
Amita Raizada ◽  
Pradeep Kothiyal
Keyword(s):  
Laser Beam ◽  
Plasma Wave ◽  
Electron Acceleration ◽  
Electron Plasma ◽  
Acceleration Process ◽  
Gaussian Laser Beam ◽  
Plasma Parameters ◽  
Electron Plasma Wave ◽  
Self Focusing ◽  
Paraxial Ray

Abstract Excitation of electron plasma wave by an intense short laser pulse is relevant to electron acceleration process in laser plasma interactions. In this work, the self-focusing of an intense cosh-Gaussian laser beam in collissionless plasma have been studied in the non-paraxial region with relativistic and ponderomotive nonlinearities. Further, the effect of self-focusing of the cosh-Gaussian laser beam on the excitation of electron plasma wave and on subsequent electron acceleration has been investigated. Analytical expressions for the beam width parameter/intensity of cosh-Gaussian laser beam and the electron plasma wave have been established and solved numerically. The energy of the accelerated electrons has also been obtained. The strong self-focusing of the cosh-Gaussian laser beam in plasmas stimulates a large amplitude electron plasma wave, which further accelerates the electrons. The well-established laser and plasma parameters have been used in numerical computation. The results have been compared with paraxial ray approximation, Gaussian profile of laser beam and only with the relativistic nonlinearity. Numerical results suggest that the focusing of the cosh-Gaussian laser beam, the amplitude of electron plasma wave, and energy gain by electrons increases in non-paraxial region, when relativistic and ponderomotive nonlinearities are simultaneously operative. In addition, it has also been observed that the electron plasma wave is driven more efficiently by a cosh-Gaussian laser beam that accelerates plasma electrons to higher energies.

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