Spatial evolution of a <i>q</i>-Gaussian laser beam in relativistic plasma

Theoretical investigation on optical self action effects of intense q-Gaussian laser beams interacting with collisionless plasmas with axial density ramp has been presented. Emphasis are put on investigating the dynamics of beam width and axial phase of the laser beam.Effect of the ellipticity of the cross section of the laser beam also has been incorporated.Using variational theory based on Lagrangian formulation nonlinear partial differential equation (P.D.E) governing the evolution of beam amplitude has been reduced to a set of coupled ordinary differential equations for the beam widths of the laser beam along the transverse directions. The evolution equation for the axial phase of the laser beam has been obtained by the Fourier transform of the amplitude structure of the laser beam from coordinate space to (k x , k y ) space. The differential equations so obtained have been solved numerically to envision the effect of laser-plasma parameters on the propagation dynamics of the laser beam.

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“…The amplitude structure over the cross section of elliptical q-Gaussian laser beam at the plane if incidence (i.e., z = 0) is given by [34,35]…”

Section: Characteristics Of Q-gaussian Laser Beammentioning

confidence: 99%

Nonlinear interaction of elliptical q-Gaussian laser beams with plasmas with axial density ramp: effect of ponderomotive force

Gupta

Kumar

2021

Opt Quant Electron

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“…Consider the propagation of a linearly polarized q ‐Gaussian laser beam

\begin{matrix} E_{3} = E_{3} ((),, r, z) e^{- ι ((), ω_{0} t - k_{0} z)} e_{x} \\ E_{3} E_{3}^{⋆} = \frac{E_{30}^{2}}{f_{3}^{2}} {(1 + \frac{r^{2}}{{italicqr}_{0}^{2} f_{3}^{2}})}^{- q} \end{matrix}

through the plasma channel. The parameter q describes the deviation of the intensity profile of the laser beam from a Gaussian distribution.…”

Section: Dielectric Function Of Plasma Channel For a Q‐gaussian Lasermentioning

confidence: 99%

Non‐linear interaction of a q‐Gaussian laser beam in a plasma channel created by the ignitor‐heater technique

Gupta

2018

Contributions to Plasma Physics

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This paper presents a theoretical investigation of the propagation characteristics of a q-Gaussian laser beam propagating through a plasma channel created by the ignitor-heater technique. The ignitor beam creates the plasma by tunnel-ionization of air. The heater beam heats the plasma electrons and establishes a parabolic channel. The third beam (q-Gaussian beam) is guided in the plasma channel under the combined effects of density non-uniformity and non-uniform ohmic heating of the plasma channel. Numerical solutions of the non-linear Schrodinger wave equation (NSWE) for the fields of laser beams are obtained with the help of the moment theory approach. Particular emphasis is placed on the dynamical variations of the spot size of the laser beams and the longitudinal phase shift of the guided beam with the distance of propagation. KEYWORDSoptical guiding, phase shift, plasma channel, q-Gaussian, self-focusing INTRODUCTIONWith the rapid development of laser technology, fueled by the advent of the chirped pulse amplification (CPA) technique, [1] ultra-intense lasers have become available, leading to a continuously extending research interest on laser-matter interactions. The laser intensity is always a key factor that decides the physical phenomena and intrinsic schemes. Currently, since the enhancement of laser power has gotten into a bottleneck at the order of 10 PW, secondary optical modulation and tight focusing of the laser beams have become important approaches to achieve higher power densities. However, the laser intensities and spot sizes coming from conventional solid-state optics are limited by the damage threshold and the diffraction effects, respectively. To overcome these limitations, pre-formed plasma channels have been proposed as a promising scheme, which can support high intensities and compensate diffraction. [2,3] As with an optical fibre, a plasma channel can provide optical guidance if the index of refraction peaks on the axis, which can be achieved with a plasma density profile that has a local minimum on the axis. To guide highly intense laser beams, plasma channels must be produced in deeply ionized gases, where the density profile cannot be changed by the guided beam through further ionization. An increase in the density on the axis would lead to ionization-induced refraction and hence negate the guiding. To meet these requirements, Volfbeyn et al. [3] developed a novel technique known as the ignitor-heater technique to create plasma channels for the long-range propagation of laser beams. The physics of guiding the laser beam is as follows: the ignitor beam creates a plasma by tunnel-ionization of an ambient gas. The heater beam heats the plasma and thereby creates a concave parabolic electron density profile so that the plasma density becomes minimum on the axis compared to that at the edges of the channel where the density is maximum. Therefore, the refractive index becomes a maximum on the axis and decreases towards the edges.When a third laser beam is passed through the plasma channel, ...

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“…The intensity distribution of the q-Gaussian laser beam along its wavefront at the plane of incidence (z ¼ 0) is given by 50,51 …”

Section: Intensity Distribution Of Q-gaussian Laser Beammentioning

confidence: 99%

Second harmonic generation by relativistic self-focusing of q-Gaussian laser beam in preformed parabolic plasma channel

Singh

Gupta

2015

Physics of Plasmas

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This paper presents an investigation of relativistic self-focusing effect of a q-Gaussian laser beam on second harmonic generation in a preformed parabolic plasma channel. An expression has been derived for density perturbation associated with the plasma wave excited by the laser beam. This in turn acts as a source of second harmonic generation. The moment theory approach has been used to derive a differential equation that governs the evolution of spot size of the laser beam with the distance of propagation. The detailed effects of intensity distribution deviation from Gaussian distribution, intensity of laser beam, density, and depth of the channel have been studied on self-focusing as well as on second harmonic generation.

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Spatial evolution of a q-Gaussian laser beam in relativistic plasma

Cited by 50 publications

References 51 publications

Nonlinear interaction of elliptical q-Gaussian laser beams with plasmas with axial density ramp: effect of ponderomotive force

Nonlinear interaction of elliptical q-Gaussian laser beams with plasmas with axial density ramp: effect of ponderomotive force

Non‐linear interaction of a q‐Gaussian laser beam in a plasma channel created by the ignitor‐heater technique

Second harmonic generation by relativistic self-focusing of q-Gaussian laser beam in preformed parabolic plasma channel

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