scholarly journals Effect of cross focusing of two laser beams on the growth of laser ripple in plasma

2003 ◽  
Vol 21 (4) ◽  
pp. 567-572 ◽  
Author(s):  
GUNJAN PUROHIT ◽  
H.D. PANDEY ◽  
R.P. SHARMA
Keyword(s):  
Laser Beam ◽  
Numerical Solution ◽  
Intensity Distribution ◽  
Laser Plasma ◽  
Dynamical Equation ◽  
Ponderomotive Force ◽  
Laser Beams ◽  
Plasma Parameters ◽  
Set Up

This article presents an effect of cross focusing of two laser beams on the growth of a laser ripple in laser-produced plasmas. The mechanism of nonlinearity is assumed to be ponderomotive force, arising because of the Gaussian intensity distribution of the laser beams. The dynamical equation governing the laser ripple intensity has been set up and a numerical solution has been presented for typical laser plasma parameters. It is found that the change in the intensity of the second laser beam can affect the growth of the laser ripple significantly.

scholarly journals On the dynamics of ponderomotive filamentation of laser beams in a plasma

1988 ◽  
Vol 6 (2) ◽  
pp. 295-304 ◽  
Author(s):  
J. Limpouch ◽  
G. Lončar ◽  
I. G. Lebo ◽  
V. B. Rozanov
Keyword(s):  
Laser Beam ◽  
Large Amplitude ◽  
Ponderomotive Force ◽  
Laser Beams ◽  
Asymptotic Value ◽  
Transient Behaviour ◽  
Plasma Motion ◽  
Plasma Response ◽  
Temporary Growth ◽  
Stationary Approximation

The influence of ponderomotive force-induced plasma motion on filamentation is examined, using both linear and non-linear descriptions. Although the time asymptote of the process is identical to the stationary convective amplification of filaments, the dynamics of the plasma response may have a serious impact on the transient behaviour of filamentation. The plasma motion contains large amplitude oscillations of inhomogeneities in the laser beam with maxima that substantially exceed the asymptotic value and temporary growth of the very narrow filaments, which cannot be amplified in the stationary approximation.

Relativistic cross-focusing of extraordinary and ordinary modes in a magnetoactive plasma

2013 ◽  
Vol 79 (5) ◽  
pp. 953-961 ◽  
Author(s):  
MEENU ASTHANA VARSHNEY ◽  
SHALINI SHUKLA ◽  
SONU SEN ◽  
DINESH VARSHNEY
Keyword(s):  
Magnetic Field ◽  
Laser Beam ◽  
Magnetoactive Plasma ◽  
Plasma Parameters ◽  
Self Focusing ◽  
Second Mode ◽  
Polarized Beam ◽  
Set Up ◽  
Overdense Plasma ◽  
The Magnetic Field

AbstractThis paper presents the effect of self-focusing on a circularly polarized beam propagating along the static magnetic field when the extraordinary and ordinary modes are present simultaneously for relativistic intensities. The nonlinearity in the dielectric function arises on account of the relativistic variation of mass, which leads to the mutual coupling of the two modes that support the self-focusing of each other. The propagation and focusing of the first mode affects the propagation and focusing of the second mode. The fact that the two modes are laser-intensity dependent leads to cross-focusing. Dynamics of one laser beam affects the dynamics of the second laser beam. When both the beams or modes are strong, the nonlinearities introduced by the relativistic effect in the presence of the magnetic field are additive in nature, such that one beam can undergo oscillatory self-focusing and other beam simultaneously defocusing and vice versa. The dynamical equation governing the cross-focusing has been set up and a numerical solution has been presented for typical relativistic laser–plasma parameters from a slightly underdense to overdense plasma.

scholarly journals A study on the effects and visibility of low-order aberrations on laser beams with orbital angular momentum

2019 ◽  
Vol 125 (11) ◽  
Author(s):  
Jonas B. Ohland ◽  
Udo Eisenbarth ◽  
Markus Roth ◽  
Vincent Bagnoud
Keyword(s):  
Angular Momentum ◽  
Laser Beam ◽  
Orbital Angular Momentum ◽  
Intensity Distribution ◽  
Laser Beams ◽  
Far Field ◽  
Wavefront Aberrations ◽  
Tolerance Criteria ◽  
Selection Of ◽  
Low Order

Abstract Laguerre–Gaussian-like laser beams have been proposed for driving experiments with high-intensity lasers. They carry orbital angular momentum and exhibit a ring-shaped intensity distribution in the far field which make them particularly attractive for various applications. We show experimentally and numerically that this donut-like shape is extremely sensitive to off-axis wavefront deformations. To support our claim, we generate a Laguerre–Gaussian-like laser beam and apply a selection of common low-order wavefront aberrations. We investigate the visibility of those wavefront deformations in the far field. Under use of established tolerance criteria, we determine the thresholds for the applied aberration and compare the findings with simulations for verification.

scholarly journals Electron plasma wave excitation by beating of two q-Gaussian laser beams in collisionless plasma

2016 ◽  
Vol 34 (2) ◽  
pp. 230-241 ◽  
Author(s):  
Arvinder Singh ◽  
Naveen Gupta
Keyword(s):  
Laser Beam ◽  
Plasma Wave ◽  
Electron Concentration ◽  
Collisionless Plasma ◽  
Electron Plasma ◽  
Spot Size ◽  
Laser Beams ◽  
Plasma Parameters ◽  
Electron Plasma Wave ◽  
Ponderomotive Nonlinearity

AbstractThis paper presents a scheme for excitation of an electron-plasma wave (EPW) by beating two q-Gaussian laser beams in an underdense plasma where ponderomotive nonlinearity is operative. Starting from nonlinear Schrödinger-type wave equation in Wentzel–Kramers–Brillouin (WKB) approximation, the coupled differential equations governing the evolution of spot size of laser beams with distance of propagation have been derived. The ponderomotive nonlinearity depends not only on the intensity of first laser beam, but also on that of second laser beam. Therefore, the dynamics of one laser beam affects that of other and hence, cross-focusing of the two laser beams takes place. Due to nonuniform intensity distribution along the wavefronts of the laser beams, the background electron concentration is modified. The amplitude of EPW, which depends on the background electron concentration, is thus nonlinearly coupled with the laser beams. The effects of ponderomotive nonlinearity and cross-focusing of the laser beams on excitation of EPW have been incorporated. Numerical simulations have been carried out to investigate the effect of laser and plasma parameters on cross-focusing of the two laser beams and further its effect on EPW excitation.

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.

scholarly journals Nonlinear Interaction of Elliptical q-Gaussian Laser Beams with Plasmas with Axial Density Ramp: Effect of Ponderomotive Force

2021 ◽  
Author(s):  
Naveen Gupta ◽  
Sandeep Kumar
Keyword(s):  
Differential Equations ◽  
Laser Beam ◽  
Nonlinear Partial Differential Equation ◽  
Beam Width ◽  
Laser Beams ◽  
Coordinate Space ◽  
Variational Theory ◽  
Plasma Parameters ◽  
The Fourier Transform ◽  
Axial Density

Abstract Theoretical investigation on optical self action effects of intense q-Gaussian laser beams interaction with collisionless plasmas with axial density ramp have been investigated in detail. 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 (kx; ky) 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.

scholarly journals Generation of Second Harmonics of Relativistically Self-Focused q-Gaussian Laser Beams in Underdense Plasma with Axial Density Ramp

2021 ◽  
Author(s):  
Naveen Gupta ◽  
Sandeep Kumar
Keyword(s):  
Laser Beam ◽  
Plasma Wave ◽  
Pump Beam ◽  
Second Harmonic ◽  
Fluid Model ◽  
Intense Laser ◽  
Laser Beams ◽  
Variational Theory ◽  
Plasma Parameters ◽  
Pump Frequency

Abstract An investigation on frequency doubling of intense laser beams through the phenomenon of second harmonic generation (SHG) in underdense plasmas has been presented. In order to increase the efficiency of S.H.G the density profile of plasma has been considered in the shape of upward ramp. When laser beam with frequency !0 propagates through plasma, it makes the plasma electrons to oscillate at pump frequency. These oscillations of plasma electrons in the presence of thermal velocity generate a plasma wave at frequency !0. The generated plasma wave beats with the pump beam to double its frequency. Variational theory has been adopted to find semi analytical solution of the wave equation for the slowly varying envelope of the laser beam. By using hydrodynamic fluid model of plasma, nonlinear current density for SHG has been obtained. Emphasis are put on investigation of the effect of various laser and plasma parameters on propagation dynamics of pump beam and the power of generated second harmonics.

scholarly journals Laser beam welding setup for the coaxial combination of two laser beams to vary the intensity distribution

2022 ◽  
Author(s):  
M. Möbus ◽  
P. Woizeschke
Keyword(s):  
Laser Beam ◽  
Penetration Depth ◽  
Intensity Distribution ◽  
Laser Beam Welding ◽  
Sample Surface ◽  
Laser Beams ◽  
Deep Penetration ◽  
Focal Position ◽  
Laser Systems ◽  
Laser Sources

AbstractDeep-penetration laser beam welding is highly dynamic and affected by many parameters. Several investigations using differently sized laser spots, spot-in-spot laser systems, and multi-focus optics show that the intensity distribution is one of the most influential parameters; however, the targeted lateral and axial intensity design remains a major challenge. Therefore, a laser processing optic has been developed that coaxially combines two separate laser sources/beams with different beam characteristics and a measuring beam for optical coherence tomography (OCT). In comparison to current commercial spot-in-spot laser systems, this setup not only makes it possible to independently vary the powers of the two laser beams but also their focal planes, thus facilitating the investigation into the influence of specific energy densities along the beam axis. First investigations show that the weld penetration depth increases with increasing intensities in deeper focal positions until the reduced intensity at the sample surface, due to the deep focal position, is no longer sufficient to form a stable keyhole, causing the penetration depth to drop sharply.

scholarly journals Beat wave excitation of electron plasma wave by coaxial cosh-Gaussian laser beams in collisional plasma

2015 ◽  
Vol 33 (4) ◽  
pp. 621-632 ◽  
Author(s):  
Arvinder Singh ◽  
Naveen Gupta
Keyword(s):  
Laser Beam ◽  
Plasma Wave ◽  
Electron Plasma ◽  
Spot Size ◽  
Collisional Plasma ◽  
Laser Beams ◽  
Theory Approach ◽  
Wave Excitation ◽  
Plasma Parameters ◽  
Electron Plasma Wave

AbstractThis paper presents a scheme for beat wave excitation of an electron plasma wave (EPW) by cross-focusing of two intense cosh-Gaussian (ChG) laser beams in an under dense collisional plasma. The plasma wave is generated on account of beating of two ChG laser beams of frequencies ω1 and ω2. Starting from Maxwell's equations, coupled differential equations governing the evolution of spot size of laser beams with distance of propagation have been derived by using Moment theory approach in Wentzel–Kramers–Brillouin approximation. The collisional nonlinearity depends not only on the intensity of first laser beam, but also on that of second laser beam. Therefore, dynamics of first laser beam affects that of other and hence cross-focusing of the two laser beams takes place. Numerical simulations have been carried out to investigate the effect of laser as well as plasma parameters on cross-focusing of laser beams and further its effect on power of excited EPW. It has been found that decentered parameters of the two laser beams have significant effect on power of EPW.

Sign in / Sign up

Export Citation Format

Share Document