Study of nonlinear ohmic heating and ponderomotive force effects on the self-focusing and defocusing of Gaussian laser beams in collisional underdense plasmas

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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Relativistic cross-focusing of two coaxial Gaussian laser beams in a plasma

Journal of Plasma Physics ◽

10.1017/s0022377898007132 ◽

1998 ◽

Vol 60 (4) ◽

pp. 811-818 ◽

Cited By ~ 13

Author(s):

RAJ KUMAR ◽

H. D. PANDEY ◽

R. P. SHARMA ◽

M. KUMAR

Keyword(s):

Laser Beam ◽

Relativistic Effect ◽

Laser Pulses ◽

The Self ◽

Laser Beams ◽

Particle Accelerators ◽

Wave Excitation ◽

Homogeneous Plasma ◽

Self Focusing ◽

Ponderomotive Nonlinearity

The paper presents a paraxial theory of the relativistic cross-focusing of two coaxial Gaussian laser beams of different frequencies in a homogeneous plasma. We discuss the self-focusing of a weaker laser beam in the plasma due to the optical inhomogeneities introduced by another stronger copropagating laser beam. In the presence of the second stronger beam (Pcr21<P2<Pcr22), the plasma behaves as an oscillatory waveguide for the first, weaker, beam (P1<Pcr11) as it propagates in the plasma. When both the beams are strong (Pcr11,21<P1,2<Pcr12,22), the nonlinearities introduced by the relativistic effect are additive in nature, such that one beam can undergo oscillatory self-focusing and the other simultaneously defocusing, and vice versa. A comparison reveals that cross-focusing due to relativistic nonlinearity is possible for a wider range of powers of the laser pulses than is cross-focusing due to ponderomotive nonlinearity. Relativistic cross-focusing is important in plasma beat-wave excitation and collective laser particle accelerators.

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Ray optics hamiltonian approach to relativistic self focusing of ultraintense lasers in underdense plasmas

EPJ Web of Conferences ◽

10.1051/epjconf/201816701003 ◽

2018 ◽

Vol 167 ◽

pp. 01003

Author(s):

Alessandro Curcio ◽

Maria Pia Anania ◽

Fabrizio Giuseppe Bisesto ◽

Massimo Ferrario ◽

Francesco Filippi ◽

...

Keyword(s):

Laser Intensity ◽

Plasma Channel ◽

Hamiltonian Formalism ◽

Point Of View ◽

The Self ◽

Hamiltonian Approach ◽

Self Focusing ◽

Ultraintense Lasers ◽

Underdense Plasmas ◽

Underdense Plasma

The relativistic self focusing of an ultraintense laser propagating through an underdense plasma is analyzed from a geometrical optics point of view, exploiting the classical hamiltonian formalism. The distribution of the laser intensity along the self-generated plasma channel is studied and compared to measurements.

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Self-focusing of asymmetric cosh-Gaussian laser beams propagating through collisionless magnetized plasma

Laser and Particle Beams ◽

10.1017/s0263034617000684 ◽

2017 ◽

Vol 35 (4) ◽

pp. 670-676 ◽

Cited By ~ 11

Author(s):

B. D. Vhanmore ◽

S. D. Patil ◽

A. T. Valkunde ◽

T. U. Urunkar ◽

K. M. Gavade ◽

...

Keyword(s):

Magnetic Field ◽

Ponderomotive Force ◽

Beam Width ◽

Magnetized Plasma ◽

Laser Beams ◽

Gaussian Beams ◽

Equation Approach ◽

Kutta Method ◽

Runge Kutta Method ◽

Self Focusing

AbstractIn this paper, self-focusing of asymmetric cosh-Gaussian laser beams in collisionless magnetized plasma has been studied. The non-linearity in dielectric constant considered herein is mainly due to the ponderomotive force. The non-linear coupled differential equations for the beam width parameters in transverse dimensions of the beam have been obtained by using WKB and paraxial approximations under parabolic equation approach. The numerical computation is completed by using fourth-order Runge–Kutta method. The effect of unlike decentered parameters in both transverse dimensions of the beam on self-focusing of cosh-Gaussian beams has been presented. Further, the effect of the static magnetic field and polarization modes of the laser has been explored.

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Focusing of Hermite-cosh-Gaussian laser beams in collisionless magnetoplasma

Laser and Particle Beams ◽

10.1017/s0263034610000297 ◽

2010 ◽

Vol 28 (2) ◽

pp. 343-349 ◽

Cited By ~ 45

Author(s):

S.D. Patil ◽

M.V. Takale ◽

S.T. Navare ◽

M.B. Dongare

Keyword(s):

Beam Width ◽

The Self ◽

Laser Beams ◽

Combined Effects ◽

Dimensionless Distance ◽

Self Focusing ◽

Mode Index ◽

Ponderomotive Nonlinearity

AbstractThis paper presents an investigation of the focusing of Hermite-cosh-Gaussian laser beams in magneto-plasma by considering ponderomotive nonlinearity. The dynamics of the combined effects of nonlinearity and spatial diffraction is presented. To highlight the nature of focusing, plot of beam-width parameter vs. dimensionless distance of propagation has been obtained. The effect of mode index and decentered parameter on the self-focusing of the beams has been discussed.

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Domains of modulation parameter in the interaction of finite Airy–Gaussian laser beams with plasma

Laser and Particle Beams ◽

10.1017/s0263034620000270 ◽

2020 ◽

Vol 38 (3) ◽

pp. 204-210

Author(s):

V. S. Pawar ◽

S. R. Kokare ◽

S. D. Patil ◽

M. V. Takale

Keyword(s):

Absorption Coefficient ◽

Collisionless Plasma ◽

Beam Width ◽

The Self ◽

Laser Beams ◽

Linear Absorption Coefficient ◽

Linear Absorption ◽

Self Focusing ◽

Modulation Parameter ◽

Paraxial Ray

AbstractIn this paper, self-focusing of finite Airy–Gaussian (AiG) laser beams in collisionless plasma has been investigated. The source of nonlinearity considered herein is relativistic. Based on the Wentzel–Kramers–Brillouin (WKB) and paraxial-ray approximations, the nonlinear coupled differential equations for beam-width parameters in transverse dimensions of AiG beams have been established. The effect of beam's modulation parameter and linear absorption coefficient on the self-focusing/defocusing of the beams is specifically considered. It is found that self-focusing/defocusing of finite AiG beams depends on the range of modulation parameter. The extent of self-focusing is found to decrease with increase in absorption.

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Self-focusing limits at the laser-plasma interaction for treatment of cataract with nanosecond and picosecond pulses

Laser and Particle Beams ◽

10.1017/s0263034600004298 ◽

1992 ◽

Vol 10 (1) ◽

pp. 163-178 ◽

Cited By ~ 5

Author(s):

Rosemarie H. Hora ◽

Hans G. L. Coster ◽

Clement J. Walter ◽

Heinrich Hora

Keyword(s):

Optical Breakdown ◽

Laser Pulses ◽

The Self ◽

Laser Beams ◽

Temperature Plasma ◽

Picosecond Pulses ◽

Laser Plasma Interaction ◽

Self Focusing ◽

Nanosecond Range ◽

Transparent Area

Laser pulses are focused in the interior of a human eye in areas of opacity to produce there an optical breakdown resulting in a high-temperature plasma, after which the filling up with liquid results in a transparent area. The empirically given limits for Q-switch laser pulses in the nanosecond range and for mode-locked pulses in the picosecond range are analyzed, and it is shown that these limits are below the self-focusing condition of laser beams in plasmas. A further analysis evaluates theoretically where the maximum limits are given in order to provide the parameters for the highest possible pulse energy that avoids damage in the eye by self-focusing.

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Relativistic and ponderomotive self-focusing of a laser pulse in magnetized plasma

Laser and Particle Beams ◽

10.1017/s0263034612000481 ◽

2012 ◽

Vol 30 (4) ◽

pp. 659-664 ◽

Cited By ~ 11

Author(s):

Anamika Sharma ◽

V.K. Tripathi

Keyword(s):

Laser Pulse ◽

Cyclotron Frequency ◽

Ponderomotive Force ◽

Beam Width ◽

Laser Frequency ◽

Electron Cyclotron ◽

The Self ◽

Magnetized Plasma ◽

Electron Cyclotron Frequency ◽

Self Focusing

AbstractThe self-focusing of an intense right circularly polarized Gaussian laser pulse in magnetized plasma is studied. The ions are taken to be immobile and relativistic mass effect is incorporated in both the plasma frequency (ωp) and the electron cyclotron frequency (ωc) while determining the ponderomotive force on electrons. The ponderomotive force causes electron expulsion when the effective electron cyclotron frequency is below twice the laser frequency. The nonlinear plasma dielectric function due to ponderomotive and relativistic effects is derived, which is then employed in beam-width parameter equation to study the self-focusing of the laser beam. From this, we estimate the importance of relativistic self-focusing in comparison with ponderomotive self-focusing at moderate laser intensities. The beam width parameter decreases with magnetic field indicating better self-focusing. When the laser intensity is very high, the relativistic gamma factor can be modeled as ${\rm \gamma} = 0.8\left({{{{\rm \omega} _c } / {\rm \omega} }} \right)+ \sqrt {1 + a_0^2 }$γ=0.8(ωc/ω)+1+a02 where ω and a0 are the laser frequency and the normalized laser field strength, respectively. The cyclotron effects on the self-focusing of laser pulse are reduced at high field strengths.

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