Propagation characteristics of Hermite-cosh-Gaussian laser beam in a rippled density plasmas

AbstractIn the present research work, the authors have investigated the self-focusing and defocusing of Hermite-cosh-Gaussian laser (HChG) beam in an inhomogeneous rippled density plasmas. By taking the relativistic non-linearity into account, an equation for envelope is set up and solved using Wentzel–Kramers–Brillouin and the paraxial ray approximation. An ordinary non-linear differential equation governing the beam width parameter as a function of propagation distance is set up for different mode structures of the beam. Further, a numerical study of this differential equation is carried for suitable set of plasma and laser parameters. The beam undergoes periodic self-focusing/defocusing due to relativistic non-linearity. We also report the comparison between self-focusing/defocusing of HChG beam in the absence and presence of density ripple. Presence of ripple does not only leads to substantial increase in self-focusing length, but also results in oscillatory character with decreasing f. In a relativistic case, strong oscillatory self-focusing and defocusing is observed. Further, self-focusing is enhanced with increased value of decentered parameter.

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

Laser and Particle Beams ◽

10.1017/s026303461800023x ◽

2018 ◽

Vol 36 (3) ◽

pp. 353-358 ◽

Cited By ~ 5

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.

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

Laser and Particle Beams ◽

10.1017/s0263034616000276 ◽

2016 ◽

Vol 34 (3) ◽

pp. 426-432 ◽

Cited By ~ 23

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.

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Dynamics of Gaussian spikes on Gaussian laser beam in relativistic plasma

Laser and Particle Beams ◽

10.1017/s0263034609990309 ◽

2009 ◽

Vol 27 (4) ◽

pp. 587-593 ◽

Cited By ~ 9

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.

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

Laser and Particle Beams ◽

10.1017/s0263034618000125 ◽

2018 ◽

Vol 36 (2) ◽

pp. 179-185 ◽

Cited By ~ 5

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.

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

Laser and Particle Beams ◽

10.1017/s0263034616000902 ◽

2017 ◽

Vol 35 (1) ◽

pp. 137-144 ◽

Cited By ~ 1

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.

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Combined influence of axial electron temperature and exponential plasma density ramp on the self-focusing of a chirped laser in plasma

Zeitschrift für Naturforschung A ◽

10.1515/zna-2020-0021 ◽

2020 ◽

Vol 75 (7) ◽

pp. 671-675

Author(s):

Niti Kant ◽

Vishal Thakur

Keyword(s):

Electron Temperature ◽

Pulse Laser ◽

Plasma Density ◽

Beam Width ◽

Spot Size ◽

Higher Order ◽

The Self ◽

Chirped Pulse ◽

Self Focusing ◽

Paraxial Ray

AbstractAn analysis of the self-focusing of highly intense chirped pulse laser under exponential plasma density ramp with higher order value of axial electron temperature has been done. Beam width parameter is derived by using paraxial ray approximation and then solved numerically. It is seen that self-focusing of chirped pulse laser is intensely affected by the higher order values of axial electron temperature. Further, influence of exponential plasma density ramp is studied and it is concluded that self-focusing of laser enhances and occurs earlier. On the other hand defocusing of beam reduces to the great extent. It is noticed that the laser spot size reduces significantly under joint influence of the density ramp and the axial electron temperature. Present analysis may be useful for the analysis of quantum dots, the laser induced fusion and etc.

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

Journal of Plasma Physics ◽

10.1017/s0022377899008016 ◽

1999 ◽

Vol 62 (4) ◽

pp. 389-396 ◽

Cited By ~ 10

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.

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Generation of Efficient Terahertz Radiation by Relativistic Self-Focusing of A Cosh-Gaussian Laser Beam in A Magnetized Plasma

10.21203/rs.3.rs-1195824/v1 ◽

2021 ◽

Author(s):

Gunjan Purohit ◽

Bineet Gaur ◽

Pradeep Kothiyal ◽

Amita Raizada

Keyword(s):

Laser Beam ◽

Numerical Study ◽

The Self ◽

Magnetized Plasma ◽

Thz Radiation ◽

Gaussian Laser Beam ◽

Plasma Parameters ◽

Gaussian Profile ◽

Self Focusing ◽

Incident Laser Intensity

Abstract This paper presents a scheme for the generation of terahertz (THz) radiation by self-focusing of a cosh-Gaussian laser beam in the magnetized and rippled density plasma, when relativistic nonlinearity is operative. The strong coupling between self-focused laser beam and pre-existing density ripple produces nonlinear current that originates THz radiation. THz radiation is produced by the interaction of the cosh-Gaussian laser beam with electron plasma wave under the appropriate phase matching conditions. Expressions for the beamwidth parameter of cosh-Gaussian laser beam and the electric vector of the THz radiation have been obtained using higher-order paraxial theory and solved numerically. The self-focusing of the cosh-Gaussian laser beam and its effect on the generated THz amplitude have been studied for specific laser and plasma parameters. Numerical study has been performed on various values of the decentered parameter, incident laser intensity, magnetic field, and relative density. The results have also been compared with the paraxial region as well as the Gaussian profile of laser beam. Numerical results suggest that the self-focusing of the cosh-Gaussian laser beam and the amplitude of THz radiation increase in the extended paraxial region compared to the paraxial region. It is also observed that the focusing of the cosh-Gaussian laser beam in the magnetized plasma and the amplitude of the THz radiation increases at higher values of the decentered parameter.

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

Laser and Particle Beams ◽

10.1017/s0263034616000525 ◽

2016 ◽

Vol 34 (4) ◽

pp. 621-630 ◽

Cited By ~ 8

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.

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Relativistic self-focusing of transmitted laser radiation in plasmas

Laser and Particle Beams ◽

10.1017/s0263034600181121 ◽

2000 ◽

Vol 18 (1) ◽

pp. 101-107 ◽

Cited By ~ 3

Author(s):

MEENU V. ASTHANA ◽

DINESH VARSHNEY ◽

M.S. SODHA

Keyword(s):

Dielectric Constant ◽

Laser Radiation ◽

Critical Power ◽

Interaction Process ◽

Gaussian Laser Beam ◽

Laser Plasma Interaction ◽

Paraxial Ray Approximation ◽

Self Focusing ◽

Beam Incident ◽

Paraxial Ray

This paper presents an analysis of relativistic self-focusing of a Gaussian laser beam incident normally on a plane interface of a linear medium and a nonlinear, nonabsorbing plasma with an intensity dependent dielectric constant. Considering the nonlinearity to arise from the relativistic variation of mass and the Lorentz force on electrons. Following Wentzel–Kramers–Brillouin (WKB) and paraxial ray approximation the phenomenon of relativistic self-focusing of the transmitted laser radiation has been analyzed for the arbitrary magnitude of nonlinearity. Change in the intensity distribution along the wavefront of the Gaussian beam, due to refraction at the interface has also been taken into account. The variation of beamwidth parameter with distance of propagation, self trapping condition and critical power has been evaluated. Numerical estimates for typical parameters of laser plasma interaction process indicate the refraction at the interface to have a significant effect on self-focusing.

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