Laser Beam In Magnetized Plasma Research Articles

The self-focusing of hollow gaussian laser beam in magnetized plasma with transverse magnetic field by operating relativistic nonlinearity

The self-focusing of hollow gaussian laser beam in magnetized plasma with transverse magnetic field by operating relativistic nonlinearity

The effect of density ramp on self-focusing of q-Gaussian laser beam in magnetized plasma

The effect of density ramp on self-focusing of q-Gaussian laser beam in magnetized plasma

Self-focusing of asymmetric finite Airy-Gaussian laser beams in magnetized plasma

Self-focusing of asymmetric finite Airy-Gaussian laser beams in magnetized plasma

Effect of an external magnetic field on the self-focusing of a cosh-Gaussian laser beam in plasma under the relativistic-ponderomotive effect

This work presents an analytical and numerical study of the relativistic-ponderomotive effect on self-focusing of an intense cosh-Gaussian laser beam in a collisionless magnetized plasma by considering an external magnetic field in the direction of propagation of the laser beam. The nonlinear differential equation for the beam width parameter/intensity of a cosh-Gaussian laser beam in a magnetized plasma is obtained by Wentzel–Kramers–Brillouin (WKB) and paraxial-ray approximations. The self-focusing of the cosh-Gaussian beam at different values of the magnetic field parameter is investigated. The results have also been compared to relativistic nonlinearity. The results show that the self-focusing effect of cosh-Gaussian beam in magnetized plasma becomes stronger, when relativistic and ponderomotive nonlinearities acts together. In addition, the self-trapping of cosh-Gaussian beam in magnetized plasma has also been studied. Numerical results are presented for the well-established laser and plasma parameters.

Strong self-focusing of an intense cosh-Gaussian laser beam in magnetized plasma under relativistic effect

Strong self-focusing of an intense cosh-Gaussian laser beam in magnetized plasma under relativistic effect

Upper hybrid wave excitation and particle acceleration by resonant beating of two hollow Gaussian laser beams in magnetized plasma

This paper investigates the excitation of the upper hybrid wave by resonant beating of two intense hollow Gaussian relativistic laser beams in a magnetized plasma. Hollow laser beams are taken in this study because they have the same power at different beam orders. The interaction of two intense hollow laser beams at the frequency difference ( Δ ω ≈ ω 1 − ω 2 ) and wavenumber ( Δ k = k 1 − k 2 ) excites the upper hybrid wave in the magnetized plasma. The excited upper hybrid wave accelerates the electrons to higher energies. The acceleration of electrons has also been studied. This study is carried out under a higher-order paraxial region, where the dielectric constant and the eikonal are expanded to the fourth power of the radial distance. Analytical expressions are obtained for the beam width parameter of the hollow Gaussian laser beams, the electric field of the upper hybrid wave, and the energy gain by the electrons. The effects of various laser and plasma parameters (such as beam order, plasma frequency, and electron cyclotron frequency) on the electric field of the upper hybrid wave and the energy gain of electrons have been explored. The results are compared with paraxial region and the Gaussian profile of laser beams. Numerical analysis has been performed for well-established laser and plasma parameters.

Propagation of two relativistic hollow Gaussian laser beams in magnetized plasma: extended paraxial theory

This work presents an analytical and numerical study for the mutual interaction and propagation of two intense hollow Gaussian laser beams (HGLBs) at difference frequency in a magnetized plasma. This work has been done in the presence of relativistic nonlinearity, which depends on the intensity of both laser beams. In this process, the propagation of both laser beams in the plasma is described by cross-focusing, as the behavior of one laser beam affects that of another laser beam. The nonlinear differential equations for the beamwidth of HGLBs have been obtained within the Wentzel–Kramers–Brillouin (WKB) method and higher-order paraxial theory. The expression for the nonlinear dielectric constant of the plasma has been obtained from the maximum irradiance of the HGLBs. The obtained equations have been solved numerically to explore the effect of the well-established laser and plasma parameters on the focusing of both laser beams in a magnetized plasma. The results have been compared with paraxial ray theory and Gaussian profile of the laser beams. The focusing/intensity of both laser beams increases in the extended paraxial region compared to the paraxial region in the magnetized plasma. The focusing of both laser beams increases even at high values of beam order and electron cyclotron frequency in the extended paraxial region.

Electron Bernstein wave excitation and heating by nonlinear interactions of Laguerre and Hermite Gaussian laser beams in a magnetized plasma

In this paper, we have studied the nonlinear interaction of Laguerre-Gaussian (LG) and Hermite-Gaussian (HG) laser beams in magnetized plasma, and electron Bernstein wave (EBW) excitation and heating of electron is evaluated. The beat wave with frequency ω=(ω1-ω2) and wave vector k→=k→1+k→2, exert a pondermotive force on electrons. This force has potential to drive electron Bernstein wave in both homogeneous and inhomogeneous plasma. The convective loss of waves in inhomogeneous plasma is discussed. An analytical theory is also developed for the anomalous heating of electrons. The variation of normalized potential and power distribution with normalized frequency and beam direction is demonstrated to excite EBWs under resonance conditions. The laser parameters such as beam width, modes index, and frequency affect the EBWs excitation and rate of electron heating. In addition, the spatial tuned shape of beams and the optimum laser beams parameter is proposed for much more exaction and heating.

Second harmonic generation of cosh-Gaussian laser beam in magnetized plasma

In the present paper, second harmonic generation (SHG) of cosh-Gaussian laser in a magnetized plasma is analyzed. During laser propagation through plasma, electrons acquire the oscillatory velocity and result density perturbation. The density oscillations beat with the oscillatory velocity to produce second harmonic current which drives SHG. Wiggler magnetic field adds the additional momentum to the photons of second harmonic and fulfills the phase matching condition which results in resonant SHG. Wiggler magnetic field also helps to maintain the cyclotron frequency due to which plasma electrons remain confined within the plasma region and results SHG of higher efficiency. Using paraxial approximation, we have derived the equation for the amplitude of SHG and studied its variation for different values of intensity parameter of incident laser, wiggler magnetic field, decentered parameter and plasma density. The efficiency of SHG is significant at higher values of intensity of incident laser, wiggler field, and plasma density as observed in our analysis.

Generation of terahertz radiation from beating of two intense cosh-Gaussian laser beams in magnetized plasma

AbstractAn analytical and numerical study has been carried out for the generation of terahertz (THz) radiation by beating of two intense cosh-Gaussian laser beams (decentered Gaussian beams) in the rippled density magnetized plasma under the relativistic–ponderomotive regime. In this process, both laser beams exert a relativistic–ponderomotive force on plasma electrons at the beat frequency and impart them an oscillatory velocity in the presence of a static magnetic field. Due to coupling between this nonlinear oscillatory velocity with density ripple, nonlinear current is generated that excites the THz radiation at the different frequency. Higher-order paraxial-ray approximation (non-paraxial theory) has been used in this study. The effects of the decentered parameter, magnetic field, and density ripple on the THz radiation generation in ripple density magnetized plasma have been investigated. Further, the effect of beating of laser beams on the THz field amplitude and the efficiency of THz radiation have been studied. The amplitude and efficiency of the emitted radiation are found to be highly sensitive to the decentered parameter, magnetic field, and density ripple. It has been found that the amplitude and efficiency of the generated THz radiation increase significantly with increasing the values of decentered parameter, magnetic field, and density ripple.

Self-focusing of higher-order asymmetric elegant Hermite-cosh-Gaussian laser beams in collisionless magnetized plasma

In the present paper, we have explored the complexity in self-focusing of asymmetric elegant Hermite-cosh-Gaussian (EHChG) laser beams in magnetized plasmas. We have studied transverse electromagnetic (TEM) mode indices (m, n) of laser with distinct values (0, 0), (0, 2) and (0, 4). The nonlinearity in dielectric constant considered herein is mainly due to the ponderomotive force. General form of differential equations for beam-width parameters in both transverse dimensions of the beam are established by using WKB and paraxial approximations through parabolic wave equation approach. The behaviour of beam-width parameters with dimensionless distance of propagation is studied at different parameters of plasma and those of the considered beams family.

Self‐focusing of a cosh‐Gaussian laser beam in magnetized plasma under relativistic‐ponderomotive regime

The combined effect of relativistic and ponderomotive nonlinearities on the self‐focusing of an intense cosh‐Gaussian laser beam (CGLB) in magnetized plasma have been investigated. Higher‐order paraxial‐ray approximation has been used to set up the self‐focusing equations, where higher‐order terms in the expansion of the dielectric function and the eikonal are taken into account. The effects of various lasers and plasma parameters viz. laser intensity (a0), decentred parameter (b), and magnetic field (ωc) on the self‐focusing of CGLB have been explored. The results are compared with the Gaussian profile of laser beams and relativistic nonlinearity. Self‐focusing can be enhanced by optimizing and selecting the appropriate laser‐plasma parameters. It is observed that the focusing of CGLB is fast in a nonparaxial region in comparison with that of a Gaussian laser beam and in a paraxial region in magnetized plasma. In addition, strong self‐focusing of CGLB is observed at higher values of a0, b, and ωc. Numerical results show that CGLB can produce ultrahigh laser irradiance over distances much greater than the Rayleigh length, which can be used for various applications.

Generation of terahertz radiation by intense hollow Gaussian laser beam in magnetised plasma under relativistic-ponderomotive regime

This paper explores the self-focusing of hollow Gaussian laser beam (HGLB) in collisionless magnetized plasma and its effect on the generation of THz radiation in the presence of relativistic-ponderomotive nonlinearity. The relativistic change of electron mass and electron density perturbation due to the ponderomotive force leads to self-focusing of the laser beam in plasma. Nonlinear coupling between the intense HGLB and electron plasma wave leads to generation of THz radiation in plasma. Resonant excitation of THz radiation at different frequencies of laser and electron plasma wave satisfies proper phase matching conditions. Appropriate expressions for the beam width parameter of the laser beam and the electric vector of the THz wave have been evaluated under the paraxial-ray and Wentzel-Kramers Brillouin approximations. It is found that the yield of THz amplitude depends on the focusing behaviour of laser beam, magnetic field, and background electron density. Numerical simulations have been carried out to investigate the effect of laser and plasma parameters on self-focusing of the laser beam and further its effect on the efficiency of the generated THz radiation.

Terahertz radiation by self-focused amplitude-modulated Gaussian laser beam in magnetized ripple density plasma

AbstractThis paper presents a theoretical model for efficient terahertz (THz) radiation by self-focused amplitude-modulated laser beam in preformed ripple density plasma. The density of plasma is modified due to ponderomotive nonlinearity which arises because of the nonuniform spatial profile of the laser beam in magnetized plasma and leads to the self-focusing of the laser beam. The rate of self-focusing depends on the intensity of the amplitude-modulated beam as well as on the externally applied magnetic field strength. The electron also experiences time-dependent ponderomotive force by the laser beam at modulated frequency. A nonlinear current at THz frequency arises on account of the coupling between the ripple density plasma and nonlinear oscillatory velocity of the electrons. The yield of the generated THz radiation enhances with enhancement in self-focusing of the laser beam and applied magnetic field.

Terahertz generation by two cross focused Gaussian laser beams in magnetized plasma

This paper presents a theoretical model for terahertz (THz) radiation generation by two cross-focused Gaussian laser beams in a collisionless magnetoplasma. The plasma is redistributed due to the ponderomotive nonlinearity which leads to the cross focusing of the laser beams. The focusing of the copropagating laser beams increases with increasing the externally applied static magnetic field which is perpendicular to the wave propagation direction. The nonlinear current at THz frequency arises on account of nonlinear ponderomotive force as a result of beating of the two lasers. The generated THz radiation amplitude increases significantly with increasing magnetic field. The cross focusing of two laser beams enhances the THz yield. Optimization of laser-plasma parameters gives the radiated normalized THz power of the order of 10 kW.

Modulation instability by intense laser beam in magnetized plasma

Modulation instability of an intense right-hand elliptically polarized laser beam propagating through magnetized plasma is investigated by a new method. The nonlinear dispersion relation, in which the relativistic and ponderomotive nonlinearities are taken into account, is obtained for the laser radiation in magnetized plasma by the Lorentz transformation. The Karpman equation is firstly generalized to the case of three dimensions with three field components. When the nonlinear frequency shift of the electromagnetic field in plasma is involved, the nonlinear evolution equation for the slowly varying envelope of the laser field is obtained. Thus, modulation instability of the intense laser beam in magnetized plasma is studied and the temporal growth rate of the instability is derived. The analysis shows that the peak growth rate of self-modulation instability is increased due to the axial magnetization of plasma. It is also shown that the growth rate of modulation instability is increased significantly near the critical surface in a laser–plasma.

Magnetically induced transparency of circularly polarized laser beam in plasmas

For the intensities greater than 1018 W/cm 2, circularly polarized radiation can propagate in electron plasma whose density is greater than the critical density. A strong flow of relativistic electrons, axially co-moving with the pulse arises. At this point the, the magnetic field of the electromagnetic wave becomes important. In the present paper, three regimes of propagation of circularly polarized laser beam in magnetized plasma are identified. An appropriate expression for the non-linear dielectric tensor has been used in the analysis under paraxial approximation. Two modes of propagation, viz, extraordinary mode and ordinary mode exist; because of the relativistic mechanism the induced magnetic field significantly affect the propagation of laser beam in plasma. Further studied for inhomogeneous plasma and penetration in overdense plasma is indicated. The induced magnetic field leads to the magnetically induced transparency due to extraordinary mode.

Propagation modes and regimes of intense laser beam in magnetized plasma

This paper presents an analytical and numerical investigation of a circularly polarized beam propagating along the static magnetic field parallel to oscillating magnetic field in plasma at relativistic intensities. In the high intensity regime, such a magnetic field is created by the pulse itself. The authors have identified three regimes of propagation taking into account the relativistic mass correction. Based on WKB and paraxial ray theory, an appropriate expression for a dielectric tensor has been evaluated in the presence of an externally applied magnetic field. The natural electromagnetic modes are circularly polarized. Consequently, extraordinary and ordinary modes propagate, which are significantly affected due to the relativistic mechanism. The regimes are characterized by dimensionless power and beamwidth, characterizing the nature of propagation as steady divergence, oscillatory divergence and self-focusing. Numerical computations are presented and discussed for typical parameters of laser plasma interaction; defined through critical parameters, namely cyclotron-to-beam frequency (Ω c ), plasma-to-beam frequency (Ω p ) and beam power for arbitrary large intensities.

Self-focusing of intense laser beam in magnetized plasma

In this paper, evolution of spot size of an intense laser beam in cold, underdense, magnetized plasma has been studied. The plasma is embedded in a uniform magnetic field perpendicular to both, the direction of propagation and electric vector of the radiation field. Nonlinear current density is set up and the source dependent expansion method is used to determine the evolution of the spot size of a laser beam having a Gaussian profile. It is shown that transverse magnetization of plasma enhances the self-focusing property of the laser beam leading to reduction in critical power required to self-focus the beam.