Self-focusing Of cosh-Gaussian Laser Beam Research Articles

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.

Influence of Magnetic field and Decentred Parameter on Self-Focusing of CoshGaussian Laser Beam in Collisional Magnetized Plasma

In the present investigation, Three-dimensional Cosh-Gaussian laser beam is introduced. The self-focusing and defocusing of Cosh-Gaussian laser beam in collisional magnetized plasma have been investigated theoretically. The final Differential equation for the beam width parameter is derived by following Wentzel-Kramer’s-Brillouin (WKB) and paraxial approximation through standard Akhmanov`s parabolic wave equation. The final results of numerical computation are presented in the plot of beam width parameters (f1 & f2) versus normalized propagation distance ( ). In present investigation the author shows nonlinear effect due to magnetic field (B0), decentered parameter (b) and plasma density on self-focusing and defocusing in collisional magnetized plasma. The results show well enhancement in beam of self-focusing.

Effect of self-focusing of an intense cosh-Gaussian laser beam on second harmonic generation in a collisionless plasma: Higher-order paraxial theory

This paper presents the study of second harmonic generation in a collisionless plasma by an intense self-focused cosh-Gaussian laser beam under the combined effect of relativistic and ponderomotive nonlinearities. The second harmonics of a cosh-Gaussian laser beam is generated by the excitation of an electron plasma wave at the pump frequency. The excited electron plasma wave coupled with the pump laser beam and generate the radiation of double frequency. This study is carried out in a higher-order paraxial ray approximation where higher order terms are taken into account in the expansion of the dielectric function and the eikonal. Nonlinear differential equations have been established for the self-focusing of cosh-Gaussian laser beam in the plasma, the generation of electron plasma wave at the pump frequency, and the second harmonic generation. Numerical simulations have been carried out to investigate the effects of laser and plasma parameters such as decentred parameter (b), incident laser intensity (a), and relative plasma density (ωp0/ω0) on the self-focusing of the cosh-Gaussian laser beam and the electric field associated with electron plasma wave and second harmonic wave. A well-established set of laser and plasma parameters have been used in numerical analysis. The results show that the focusing of the cosh-Gaussian laser beam leads to an increase in the electric field of the electron plasma wave and the second harmonic wave. The results are also compared to the paraxial-ray approximation. The focusing of the cosh-Gaussian laser beam in the plasma is strengthened in the higher-order paraxial region, which increases the electric field of both the electron plasma wave and the second harmonic wave at high values of b, a, and ωp0/ω0.

Comparative Additional Factor for Diffraction Loss On (TEM01) Mode from That of (TEM00) Mode

Comparative Additional Factor for Diffraction Loss On (TEM01) Mode from That of (TEM00) Mode

Relativistic self-focusing of cosh-Gaussian laser beams in a warm quantum plasma

This paper presents an investigation of the self-focusing of cosh-Gaussian laser beams in warm quantum plasma while taking into account the effects of relativistic nonlinearity. The non-linear differential equation governing the beam width parameter under the weakly relativistic nonlinearity in this study was derived from the cylindrical coordinate system. The equation has been solved numerically by using the fourth-order Runge–Kutta method. Numerical analysis has shown that the present model's parameters, such as the decentered parameter, laser intensity, electron density of plasma, and Fermi temperature of electrons, play a vital role in propagation characteristics. Furthermore, comparisons were made for the cosh-Gaussian laser self-focusing in warm quantum plasma, cold quantum plasma, and classical relativistic plasma. It has also been found that the cosh-Gaussian laser beam has caused better focusing in the warm quantum plasma in comparison with the Gaussian laser beam; a fact that is very important for some applications in high-power laser-dense plasma interactions.

Self-focusing of cosh-Gaussian laser beam in collisional plasma: effect of nonlinear absorption

Self-focusing of cosh-Gaussian laser beam in collisional plasma: effect of nonlinear absorption

Self-focusing of cosh-Gaussian laser beam and its effect on the excitation of ion-acoustic wave and stimulated Brillouin backscattering in collisionless plasma

An analytical and numerical study has been carried out for self-focusing of an intense cosh-Gaussian laser beam in collisionless plasma and its impact on the excitation of ion-acoustic wave and stimulated Brillouin backscattering process. The analytical model has been developed under Wentzel–Kramers–Brillouin and paraxial ray approximations. The nonlinearities of ponderomotive force on electron and the relativistic oscillation of the electron mass have been used in this study. The nonlinear differential equations have been set up for the beam width parameters of the main beam, ion-acoustic wave, backscattered wave and back reflectivity of stimulated Brillouin scattering (SBS). These equations have been solved numerically for different values of decentred parameter (b), relative plasma density (ωp0/ω0) and incident laser intensity (a). The results have been compared with only relativistic nonlinearity and Gaussian profile of laser beam. The focusing of laser beam, ion-acoustic wave and scattered wave are found to be strong under relativistic-ponderomotive regime compared to only relativistic regime. Further, it is observed that focusing/intensity of main laser beam, ion acoustic wave and SBS back reflectivity increases with increasing the values of b and ωp0/ω0. Itis also found that back reflectivity of SBS process gets suppressed with the increase in the value of a. This study may be useful in laser induced fusion scheme where back scattering of SBS plays very important role.

Stronger self-focusing of cosh-Gaussian laser beam under exponential density ramp in plasma with linear absorption

A theoretical model is purposed which explains propagation of the cosh-Gaussian laser beam in the plasma with exponential density transition. Also the influence of linear absorption on self-focusing of the beam is taken into account and it may be helpful in achieving enhanced self-focusing of laser beam. The nonlinearity arises because of the relativistic motion of electrons, is considered for the penetration of laser in plasma. By considering the expression of dielectric function, we have set up differential equation for the beam width parameter. Further, the effect of decentred parameter is studied which results in stronger self-focusing of cosh-Gaussian laser beam. Stronger self-focusing of laser beam is also noticed on account of the increased plasma frequency.

Effect of Critical Beam Radius on Self-focusing of cosh-Gaussian Laser Beams in Collisionless Magnetized Plasma

Effect of critical beam radius on self-focusing of cosh-Gaussian laser beams in collisionless magnetized plasma under ponderomotive nonlinearity forms the main core of present work. To investigate propagation dynamics of cosh-Gaussian laser beams in collisionless magnetized plasma, well established parabolic equation approach under WKB and paraxial approximations is employed. Our study is crucially pivoted on the concept of critical curve and subsequent determination of numerical interval for decentered parameter to sustain the competition between diffraction and self-focusing during the propagation of laser beam. Additionally, in the present study an interesting feature in the self-focusing region of the critical curve has been attempted for different values of decentered parameter.

On the exploration of graphical and analytical investigation of effect of critical beam power on self-focusing of cosh-Gaussian laser beams in collisionless magnetized plasma

AbstractThe paper gives graphical and analytical investigation of the effect of critical beam power on self-focusing of cosh-Gaussian laser beams in collisionless magnetized plasma under ponderomotive non-linearity. The standard Akhmanov's parabolic equation approach under Wentzel–Kramers–Brillouin (WKB) and paraxial approximations is employed to investigate the propagation of cosh-Gaussian laser beams in collisionless magnetized plasma. Especially, the concept of numerical intervals and turning points of critical beam power has evolved through graphical analysis of beam-width parameter differential equation of cosh-Gaussian laser beams. The results are discussed in the light of numerical intervals and turning points.

Early and strong relativistic self-Focusing of cosh-Gaussian laser beam in cold quantum plasma

Relativistic self-focusing of cosh-Gaussian laser beam in the cold quantum plasma has been investigated theoretically. For a decentered parameter b=0.9, we present a comparative analysis for self-focusing of cosh-Gaussian laser beam in relativistic cold quantum (RCQ) and classical relativistic (CR) case. It is observed that as the beam penetrates deeper inside the RCQ plasma, the self-focusing ability of the laser beam enhances and shifted towards lower value of normalized propagation distance due to quantum contribution. The beam width parameter as a function of normalized propagation distance for various values of relative density parameter of the medium and intensity parameter has also been studied. The self-focusing is observed to be stronger with the increase in relative density parameter. Observation of early and strong self-focusing for higher values of relative density parameter and intensity parameter are reported. The present study might be very useful in the applications like the generation of inertial fusion energy driven by lasers, laser driven accelerators, scribing type of applications in electronics etc.

Second-harmonic generation by relativistic self-focusing of cosh-Gaussian laser beam in underdense plasma

AbstractThis paper presents theoretical investigation of effect of relativistic self-focusing of cosh-Gaussian (ChG) laser beam on second-harmonic generation in an underdense plasma. Steep transverse density gradients are produced in the plasma by the electron plasma wave excited by relativistic self-focusing of ChG laser beam. The generated plasma wave interacts with the pump beam to produce its second harmonics. Following Jeffrey Wentzel Kramers Brillouin (J.W.K.B) approximation and moment theory the differential equation governing the evolution of spot size of laser beam with distance of propagation has been derived. The differential equation so obtained has been solved numerically by the Runge–Kutta method to investigate the effect of decentered parameter, intensity of laser beam as well as density of plasma on self-focusing of the ChG laser beam, and generation of its second harmonics. It has been observed that the peak intensity of the laser beam shifts in the transverse direction by changing the decentered parameter and a noticeable change is observed on focusing of the laser beam as well as on conversion efficiency of second harmonics.

Density Transition Based Self-Focusing of cosh-Gaussian Laser Beam in Plasma with Linear Absorption* *Supported by a Financial Grant from CSIR, New Delhi, India, under Project No. 03(1277)/13/EMR-II

Density transition based self-focusing of cosh-Gaussian laser beam in plasma with linear absorption has been studied. The field distribution in the plasma is expressed in terms of beam width parameter, decentered parameter, and linear absorption coefficient. The differential equation for the beam width parameter is solved by following Wentzel–Kramers–Brillouin (WKB) and paraxial approximation through parabolic wave equation approach. The behaviour of beam width parameter with dimensionless distance of propagation is studied at optimum values of plasma density, decentered parameter and with different absorption levels in the medium. The results reveal that these parameters can affect the self-focusing significantly.

Strong self-focusing of a cosh-Gaussian laser beam in collisionless magneto-plasma under plasma density ramp

The effect of plasma density ramp on self-focusing of cosh-Gaussian laser beam considering ponderomotive nonlinearity is analyzed using WKB and paraxial approximation. It is noticed that cosh-Gaussian laser beam focused earlier than Gaussian beam. The focusing and de-focusing nature of the cosh-Gaussian laser beam with decentered parameter, intensity parameter, magnetic field, and relative density parameter has been studied and strong self-focusing is reported. It is investigated that decentered parameter “b” plays a significant role for the self-focusing of the laser beam as for b=2.12, strong self-focusing is seen. Further, it is observed that extraordinary mode is more prominent toward self-focusing rather than ordinary mode of propagation. For b=2.12, with the increase in the value of magnetic field self-focusing effect, in case of extraordinary mode, becomes very strong under plasma density ramp. Present study may be very useful in the applications like the generation of inertial fusion energy driven by lasers, laser driven accelerators, and x-ray lasers. Moreover, plasma density ramp plays a vital role to enhance the self-focusing effect.

Relativistic self-focusing of cosh-Gaussian laser beams in a plasma

In the present paper, we have proposed to exploit an analysis of a self-consistent, steady state, theoretical model, which explains the propagation of cosh-Gaussian laser beams in a plasma. The nonlinearity we have considered is of relativistic type. Using the expression for the dielectric function, we have setup the differential equation for beam-width parameter using the WKB and paraxial approximations. The effect of decentred parameter of the beam on the critical curve and the dependence of the beam-width on the distance of propagation have been specifically considered. The results have been presented in the form of graphs and discussed.

Self-focusing of cosh-Gaussian laser beam in a plasma with weakly relativistic and ponderomotive regime

This paper presents an investigation of the self-focusing of cosh-Gaussian laser beam in a plasma with linear absorption taking into account the combined effects of relativistic and ponderomotive type nonlinearities. Nonlinear parabolic partial differential equation governing the evolution of complex envelope in slowly varying envelope approximation is solved using variational approach. Self-focusing and self-phase modulation as well as self-trapping of cosh-Gaussian beam are studied at various values of decentered parameter b, with different absorption levels ki′. Numerical analysis shows that these parameters play vital role on propagation characteristics.

Self-focusing of cosh-Gaussian laser beams in a parabolic medium with linear absorption

The authors have investigated self-focusing of cosh-Gaussian laser beams in a parabolic medium with linear absorption. The field distribution in the medium is expressed in terms of beam-width parameter f, decentred parameter b and absorption coefficient k i . The differential equation for f parameter is established by following Wentzel–Kramers–Brillouin (WKB) and paraxial approximations through parabolic wave equation approach and analytical solution is obtained for the same. The behavior of f parameter with the normalized distance of propagation η is studied at various values of b with different absorption levels in the medium. The results are presented graphically and discussed.