Study of self-focusing of Non Gaussian laser beam in a plasma with density variation using moment theory approach

In the present paper, the effect of self-focusing on stimulated Raman scattering (SRS) process by a Gaussian laser beam in collisional plasma is investigated. Due to non-uniform heating, collisional nonlinearity arises, which leads to redistribution of carriers. As a result of which, background plasma density profile in a direction transverse to pump beam axis is modified. This modification affects the incident laser beam, electron plasma wave and back-scattered beam. Nonlinear differential equations for the beam width parameters of the main beam, electron plasma wave, back-scattered wave have been set up by taking full nonlinear part of the dielectric constant of collisional plasma with the help of moment theory approach and are solved numerically by Runge–Kutta method. It is observed from the analysis that focusing of waves greatly enhances the SRS reflectivity.

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Enhanced Brillouin scattering of gaussian laser beam in collisional plasma: Moment theory approach

Journal of Nonlinear Optical Physics & Materials ◽

10.1142/s0218863514500118 ◽

2014 ◽

Vol 23 (01) ◽

pp. 1450011 ◽

Cited By ~ 10

Author(s):

Keshav Walia

Keyword(s):

Acoustic Wave ◽

Laser Beam ◽

Pump Beam ◽

Brillouin Scattering ◽

Scattered Wave ◽

Theory Approach ◽

Gaussian Laser Beam ◽

Moment Theory ◽

Ion Acoustic Wave ◽

Ion Acoustic

In the present paper, enhanced Brillouin scattering of a gaussian laser beam in a collisional plasma has been investigated with the help of moment theory approach. The pump wave (ω0, k0) interacts with pre-excited ion-acoustic wave (ω, k), thereby generating a back-scattered wave (ω0 - ω, k0 - k). As a specific case, back scattering for which k ≃ 2k0 has been discussed. Due to nonuniform heating, collisional nonlinearity arises, which leads to redistribution of carriers. As a result background plasma density profile in a direction transverse to pump beam axis is modified. Consequently, the pump beam becomes self-focused and in turn leads focusing of ion-acoustic wave and back-scattered wave under appropriate conditions. It is further observed from the analysis that focusing of waves greatly enhances the SBS back-reflectivity.

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Self-focusing of cosh-Gaussian laser beam in collisional plasma: effect of nonlinear absorption

Journal of Optics ◽

10.1007/s12596-021-00738-3 ◽

2021 ◽

Author(s):

Naveen Gupta ◽

Sandeep Kumar ◽

A Gnaneshwaran ◽

Sanjeev Kumar ◽

Suman Choudhry

Keyword(s):

Laser Beam ◽

Nonlinear Absorption ◽

Collisional Plasma ◽

Gaussian Laser Beam ◽

Self Focusing ◽

Plasma Effect

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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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