scholarly journals Effect of self-focused rippled laser beam on the excitation of ion acoustic wave in relativistic ponderomotive regime

2014 ◽  
Vol 32 (4) ◽  
pp. 557-568 ◽  
Author(s):  
Rakhi Gauniyal ◽  
Prashant Chauhan ◽  
Priyanka Rawat ◽  
Gunjan Purohit
Keyword(s):  
Acoustic Wave ◽  
Laser Beam ◽  
Collisionless Plasma ◽  
Plasma Parameters ◽  
Power Flux ◽  
Ion Acoustic Wave ◽  
Coupled Equations ◽  
Increase With Increase ◽  
Ion Acoustic ◽  
Paraxial Ray

AbstractThis paper presents an investigation of self-focusing of intense Gaussian rippled laser beam in collisionless plasma by including the nonlinearity associated with the relativistic mass and the ponderomotive force and its effects on the excitation of ion acoustic wave. The growth of ripple, riding on an intense Gaussian laser beam in plasma and its coupling with ion acoustic wave has also been studied. Modified coupled equations for main laser beam, growth of laser ripple in plasma, rippled laser beam, beam width, and density perturbation associated with ion acoustic wave are derived using Wentzel-Kramers-Brillouin and paraxial ray approximation. These coupled equations are solved analytically and numerically to study the laser intensity in plasma and the variation of amplitude of the ion acoustic wave for various established laser and plasma parameters. From numerical computation, it is observed that both nonlinearities significantly affected the dynamics of the growth of laser ripple in plasma, propagation of rippled laser beam as well as ion acoustic wave in plasma at high laser power flux. The growth of laser ripple increase with increase in the intensity of laser beam and due to the contribution of growth rate, intensity profile of rippled laser beam and ion acoustic wave modified accordingly.

scholarly journals Stimulated Brillouin backscattering of a ring-rippled laser beam in collisionless plasma

2015 ◽  
Vol 33 (3) ◽  
pp. 499-509 ◽  
Author(s):  
Gunjan Purohit ◽  
Priyanka Rawat
Keyword(s):  
Laser Beam ◽  
Narrow Range ◽  
Brillouin Scattering ◽  
Collisionless Plasma ◽  
Plasma Parameters ◽  
Ion Acoustic Wave ◽  
Coupled Equations ◽  
Ion Acoustic ◽  
Paraxial Ray ◽  
Stimulated Brillouin

AbstractThe effect of the propagation of a ring-rippled laser beam in the presence of relativistic and ponderomotive non-linearities on the excitation of ion-acoustic wave (IAW) and resulting stimulated Brillouin backscattering in collisionless plasma at relativistic powers is studied. To understand the nature of propagation of the ring ripple-like instability, a paraxial-ray approach has been invoked in which all the relevant parameters correspond to a narrow range around the irradiance maximum of the ring ripple. Modified coupled equations for growth of ring ripple in the plasma, generations of IAW and back-stimulated Brillouin scattering (SBS) are derived from fluid equations. These coupled equations are solved analytically and numerically to study the intensity of ring-rippled laser beam and excited IAW as well as back reflectivity of SBS in the plasma for various established laser and plasma parameters. It is found that the back reflectivity of SBS is enhanced due to the strong coupling between ring-rippled laser beam and the excited IAW. The results also show that the back reflectivity of SBS reduce for higher intensity of the laser beam.

scholarly journals Stimulated Brillouin backscattering of hollow Gaussian laser beam in collisionless plasma under relativistic–ponderomotive regime

2016 ◽  
Vol 35 (1) ◽  
pp. 81-91 ◽  
Author(s):  
R. Gauniyal ◽  
N. Ahmad ◽  
P. Rawat ◽  
B. Gaur ◽  
S.T. Mahmoud ◽  
...  
Keyword(s):  
Acoustic Wave ◽  
Laser Beam ◽  
Collisionless Plasma ◽  
Main Beam ◽  
Theory Approach ◽  
Gaussian Laser Beam ◽  
Ion Acoustic Wave ◽  
Coupled Equations ◽  
Ion Acoustic ◽  
Stimulated Brillouin

AbstractStimulated Brillouin backscattering of an intense hollow Gaussian laser beam (HGLB) from collisionless plasma has been investigated under relativistic–ponderomotive regime. The main feature of considered hollow Gaussian laser beam is having the same power at different beam orders with null intensity at the center. Backscattered radiation is generated due to nonlinear interaction between main beam (pump beam) with pre-excited ion acoustic wave (IAW). Modified coupled equations has been set up for the beam width parameters of the main beam, ion-acoustic wave, back-scattered wave, and back reflectivity of stimulated Brillouin scattering (SBS) with the help of the Wentzel–Kramers–Brillouin approximation, fluid equations and paraxial theory approach. These coupled equations are solved analytically and numerically to study the laser intensity in the plasma, the variation of amplitude of the excited IAW and back reflectivity of SBS. The back reflectivity of SBS is found to be highly sensitive to the order of the HGLB, intensity of main laser beam, and plasma density for typical laser and plasma parameters. The focusing of main laser beam (hollow Gaussian) and IAW significantly affected the back reflectivity of SBS. The results show that the self-focusing and back reflectivity is enhanced for higher order modes of HGLB.

scholarly journals Suppression of stimulated Brillouin scattering in laser beam hot spots

2009 ◽  
Vol 27 (4) ◽  
pp. 619-627 ◽  
Author(s):  
R.P. Sharma ◽  
Prerana Sharma ◽  
Shivani Rajput ◽  
A.K. Bhardwaj
Keyword(s):  
Laser Beam ◽  
Brillouin Scattering ◽  
Collisionless Plasma ◽  
Stimulated Brillouin Scattering ◽  
Landau Damping ◽  
Beam Radius ◽  
Plasma Parameters ◽  
Power Flux ◽  
Ion Acoustic Wave ◽  
Stimulated Brillouin

AbstractIn this article, filamentation of a high power laser beam in hot collisionless plasma is investigated considering the ponderomotive nonlinearity. We have studied the effect of self focusing (filamentation) of the laser beam on the localization of ion acoustic wave (IAW) and on stimulated Brillouin scattering (SBS) process. The nonlinear coupling between the laser beam and IAW results in the modification of the Eigen frequency of IAW; consequently, enhanced Landau damping of IAW and a modified mismatch factor in SBS process occur. Due to enhanced Landau damping, there is a reduction in the intensity of IAW wave, and the SBS process gets suppressed. For the typical laser plasma parameters: the laser power flux = 1016 W/cm2, laser beam radius (r0) = 12 µm, n/ncr = 0.11, and (Te/Ti) = 10, the SBS reflectivity is found to be suppressed approximately by 10%.

scholarly journals Stimulated Brillouin backscattering of filamented hollow Gaussian beams

2013 ◽  
Vol 31 (4) ◽  
pp. 689-696 ◽  
Author(s):  
R.P. Sharma ◽  
Ram Kishor Singh
Keyword(s):  
Acoustic Wave ◽  
Gaussian Beam ◽  
Brillouin Scattering ◽  
Collisionless Plasma ◽  
Stimulated Brillouin Scattering ◽  
Ion Acoustic Wave ◽  
Ion Acoustic ◽  
Paraxial Ray ◽  
Stimulated Brillouin ◽  
Plasma Coupling

AbstractThis paper presents an investigation for excitation of ion acoustic wave and resulting stimulated Brillouin scattering in a collisionless plasma due to presence of a laser beam carrying null intensity at center (hollow Gaussian beam). In presence of ponderomotive nonlinearity, the pump beam get focused and affects the back stimulated Brillouin scattering process. To understand the nature of laser plasma coupling, a paraxial-ray approximation has been invoked for the propagation of the hollow Gaussian beam, ion acoustic wave, and stimulated Brillouin scattering. It is observed from the result that self-focusing and back reflectivity reduces for higher order of hollow Gaussian beam.

Effect of rippled laser beam on excitation of ion acoustic wave

Pramana ◽  
2000 ◽  
Vol 55 (5-6) ◽  
pp. 803-811 ◽  
Author(s):  
Nareshpal Singh Saini ◽  
Tarsem Singh Gill
Keyword(s):  
Acoustic Wave ◽  
Laser Beam ◽  
Ion Acoustic Wave ◽  
Ion Acoustic

scholarly journals Controlled beat-wave Brillouin scattering in the ionosphere

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
B. Eliasson ◽  
A. Senior ◽  
M. Rietveld ◽  
A. D. R. Phelps ◽  
R. A. Cairns ◽  
...  
Keyword(s):  
Acoustic Wave ◽  
Ionospheric Plasma ◽  
Brillouin Scattering ◽  
Scale Model ◽  
Plasma Parameters ◽  
Ion Acoustic Wave ◽  
Electromagnetic Pump ◽  
Pump And Probe ◽  
Ion Acoustic ◽  
Stimulated Brillouin

AbstractStimulated Brillouin scattering experiments in the ionospheric plasma using a single electromagnetic pump wave have previously been observed to generate an electromagnetic sideband wave, emitted by the plasma, together with an ion- acoustic wave. Here we report results of a controlled, pump and probe beat-wave driven Brillouin scattering experiment, in which an ion-acoustic wave generated by the beating of electromagnetic pump and probe waves, results in electromagnetic sideband waves that are recorded on the ground. The experiment used the EISCAT facility in northern Norway, which has several high power electromagnetic wave transmitters and receivers in the radio frequency range. An electromagnetic pump consisting of large amplitude radio waves with ordinary (O) or extraordinary (X) mode polarization was injected into the overhead ionosphere, along with a less powerful probe wave, and radio sideband emissions observed on the ground clearly show stimulated Brillouin emissions at frequencies agreeing with, and changing with, the pump and probe frequencies. The experiment was simulated using a numerical full-scale model which clearly supports the interpretation of the experimental results. Such controlled beat-wave experiments demonstrate a way of remotely investigating the ionospheric plasma parameters.

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

2014 ◽  
Vol 23 (01) ◽  
pp. 1450011 ◽  
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.

Cross Focusing of two Coaxial Gaussian Beams with Relativistic and Ponderomotive Nonlinearity

2012 ◽  
Vol 67 (1-2) ◽  
pp. 10-14
Author(s):  
Prerana Sharma
Keyword(s):  
Laser Beam ◽  
Collisionless Plasma ◽  
Laser Beams ◽  
Fourth Power ◽  
Gaussian Beams ◽  
Wave Processes ◽  
Plasma Parameters ◽  
Ponderomotive Nonlinearity ◽  
Paraxial Ray ◽  
Pump Laser Beam

This paper presents the cross focusing of two high power lasers by taking off-axial contributions of the laser beams in a collisionless plasma. Due to relativistic and ponderomotive nonlinearities the two laser beams affect the dynamics of each other and cross focusing takes place. The expressions for the laser beam intensities by using the eikonal method are derived. The contributions of the r2 and r4 terms are incorporated. By expanding the eikonal and the other relevant quantities up to the fourth power of r, the solution of the pump laser beam is obtained within the extended paraxial ray approximation. Filamentary structures of the laser beams are observed due to the relativistic and the ponderomotive nonlinearity. The focusing of the laser beams is shown to become fast in the extended paraxial region. Using the laser beam and the plasma parameters, appropriate for beat wave processes, the filaments of the laser beams are studied and the relevance of these results to beat wave processes is pointed out.

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