Generation of Efficient Terahertz Radiation by Relativistic Self-Focusing of A Cosh-Gaussian Laser Beam in A Magnetized Plasma

2021 ◽  
Author(s):  
Gunjan Purohit ◽  
Bineet Gaur ◽  
Pradeep Kothiyal ◽  
Amita Raizada
Keyword(s):  
Laser Beam ◽  
Numerical Study ◽  
The Self ◽  
Magnetized Plasma ◽  
Thz Radiation ◽  
Gaussian Laser Beam ◽  
Plasma Parameters ◽  
Gaussian Profile ◽  
Self Focusing ◽  
Incident Laser Intensity

Abstract This paper presents a scheme for the generation of terahertz (THz) radiation by self-focusing of a cosh-Gaussian laser beam in the magnetized and rippled density plasma, when relativistic nonlinearity is operative. The strong coupling between self-focused laser beam and pre-existing density ripple produces nonlinear current that originates THz radiation. THz radiation is produced by the interaction of the cosh-Gaussian laser beam with electron plasma wave under the appropriate phase matching conditions. Expressions for the beamwidth parameter of cosh-Gaussian laser beam and the electric vector of the THz radiation have been obtained using higher-order paraxial theory and solved numerically. The self-focusing of the cosh-Gaussian laser beam and its effect on the generated THz amplitude have been studied for specific laser and plasma parameters. Numerical study has been performed on various values of the decentered parameter, incident laser intensity, magnetic field, and relative density. The results have also been compared with the paraxial region as well as the Gaussian profile of laser beam. Numerical results suggest that the self-focusing of the cosh-Gaussian laser beam and the amplitude of THz radiation increase in the extended paraxial region compared to the paraxial region. It is also observed that the focusing of the cosh-Gaussian laser beam in the magnetized plasma and the amplitude of the THz radiation increases at higher values of the decentered parameter.

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

2015 ◽  
Vol 33 (4) ◽  
pp. 741-747 ◽  
Author(s):  
Ram Kishor Singh ◽  
R. P. Sharma
Keyword(s):  
Magnetic Field ◽  
Laser Beam ◽  
Applied Magnetic Field ◽  
Magnetized Plasma ◽  
Thz Radiation ◽  
Gaussian Laser Beam ◽  
Spatial Profile ◽  
Self Focusing ◽  
Oscillatory Velocity ◽  
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.

Relativistic self-focusing of a rippled laser beam in a plasma

1999 ◽  
Vol 62 (4) ◽  
pp. 389-396 ◽  
Author(s):  
M. V. ASTHANA ◽  
A. GIULIETTI ◽  
DINESH VARSHNEY ◽  
M. S. SODHA
Keyword(s):  
Refractive Index ◽  
Laser Beam ◽  
The Self ◽  
Laser Beams ◽  
Radial Dependence ◽  
Main Beam ◽  
Gaussian Laser Beam ◽  
Self Focusing ◽  
Saturation Effects ◽  
Paraxial Ray

This paper presents an analysis of the relativistic self-focusing of a rippled Gaussian laser beam in a plasma. Considering the nonlinearity as arising owing to relativistic variation of mass, and following the WKB and paraxial-ray approximations, the phenomenon of self-focusing of rippled laser beams is studied for arbitrary magnitude of nonlinearity. Pandey et al. [Phys. Fluids82, 1221 (1990)] have shown that a small ripple on the axis of the main beam grows very rapidly with distance of propagation as compared with the self-focusing of the main beam. Based on this analogy, we have analysed relativistic self-focusing of rippled beams in plasmas. The relativistic intensities with saturation effects of nonlinearity allow the nonlinear refractive index in the paraxial regime to have a slower radial dependence, and thus the ripple extracts relatively less energy from its neighbourhood.

scholarly journals Effect of self-focused cosh Gaussian laser beam on the excitation of electron plasma wave and particle acceleration

2016 ◽  
Vol 34 (4) ◽  
pp. 621-630 ◽  
Author(s):  
B. Gaur ◽  
P. Rawat ◽  
G. Purohit
Keyword(s):  
Particle Acceleration ◽  
Laser Beam ◽  
Plasma Wave ◽  
Electron Plasma ◽  
The Self ◽  
Acceleration Process ◽  
Gaussian Laser Beam ◽  
Electron Plasma Wave ◽  
Self Focusing ◽  
Paraxial Ray

AbstractThis work presents an investigation of the self-focusing of a high-power laser beam having cosh Gaussian intensity profile in a collissionless plasma under weak relativistic-ponderomotove (RP) and only relativistic regimes and its effect on the excitation of electron plasma wave (EPW), and particle acceleration process. Nonlinear differential equations have been set up for the beam width and intensity of cosh Gaussian laser beam (CGLB) and EPW using the Wentzel-Kramers-Brillouin and paraxial-ray approximations as well as fluid equations. The numerical results are presented for different values of decentered parameter ‘b’ and intensity parameter ‘a’ of CGLB. Strong self-focusing is observed in RP regime as compared with only relativistic nonlinearity. Numerical analysis shows that these parameters play crucial role on the self-focusing of the CGLB and the excitation of EPW. It is also found that the intensity/amplitude of EPW increases with b and a. Further, nonlinear coupling between the CGLB and EPW leads to the acceleration of electrons. The intensity of EPW and energy gain by electrons is significantly affected by including the ponderomotive nonlinearity. The energy of the accelerated electrons is increased by increasing the value of ‘b’. The results are presented for typical laser and plasma parameters.

scholarly journals Weakly relativistic self-focusing of Gaussian laser beam in magnetized cold quantum plasma

2017 ◽  
Vol 35 (4) ◽  
pp. 699-705 ◽  
Author(s):  
M. Aggarwal ◽  
V. Goyal ◽  
Richa ◽  
H. Kumar ◽  
T.S. Gill
Keyword(s):  
Magnetic Field ◽  
Laser Beam ◽  
Interparticle Distance ◽  
Beam Propagation ◽  
Magnetized Plasma ◽  
Quantum Plasma ◽  
Computational Technique ◽  
Gaussian Laser Beam ◽  
Self Focusing ◽  
Paraxial Ray

AbstractIn the present paper, we have studied self-focusing of Gaussian laser beam in weakly relativistic magnetized cold quantum plasma. When interparticle distance is comparable to the de Broglie wavelength of charged particles, we cannot neglect the quantum contribution of plasma constituents. Therefore, propagation characteristics are studied by taking in to account quantum contribution in the presence of static magnetic field applied along the beam propagation. Our results show that the magnetic field plays a key role in achieving additional focusing, it modifies the quiver motion of electrons by adding cyclotron frequency to the natural frequency of oscillating electrons during laser beam propagation. The results are compared with those of weakly relativistic quantum plasma and weakly relativistic magnetized plasma. The self-focusing is found to be more pronounced when axial magnetic field is increased in the present model. We have setup the non-linear differential equation for the evolution of beam-width parameter by well-known paraxial ray approximation and solved it with the help of computational technique.

Effect of light absorption and critical beam power on self-focusing of Gaussian laser beam in collision less magnetized plasma

2019 ◽  
Author(s):  
T. U. Urunkar ◽  
K. M. Gavade ◽  
B. D. Vhanmore ◽  
A. T. Valkunde ◽  
S. D. Patil ◽  
...  
Keyword(s):  
Laser Beam ◽  
Light Absorption ◽  
Magnetized Plasma ◽  
Beam Power ◽  
Gaussian Laser Beam ◽  
Self Focusing ◽  
Effect Of Light

scholarly journals Direct Electron Acceleration By An Intense Nonparaxial Cosh-Gaussian Laser Beam Driven Electron Plasma Wave in Plasma

2021 ◽  
Author(s):  
Gunjan Purohit ◽  
Bineet Gaur ◽  
Amita Raizada ◽  
Pradeep Kothiyal
Keyword(s):  
Laser Beam ◽  
Plasma Wave ◽  
Electron Acceleration ◽  
Electron Plasma ◽  
Acceleration Process ◽  
Gaussian Laser Beam ◽  
Plasma Parameters ◽  
Electron Plasma Wave ◽  
Self Focusing ◽  
Paraxial Ray

Abstract Excitation of electron plasma wave by an intense short laser pulse is relevant to electron acceleration process in laser plasma interactions. In this work, the self-focusing of an intense cosh-Gaussian laser beam in collissionless plasma have been studied in the non-paraxial region with relativistic and ponderomotive nonlinearities. Further, the effect of self-focusing of the cosh-Gaussian laser beam on the excitation of electron plasma wave and on subsequent electron acceleration has been investigated. Analytical expressions for the beam width parameter/intensity of cosh-Gaussian laser beam and the electron plasma wave have been established and solved numerically. The energy of the accelerated electrons has also been obtained. The strong self-focusing of the cosh-Gaussian laser beam in plasmas stimulates a large amplitude electron plasma wave, which further accelerates the electrons. The well-established laser and plasma parameters have been used in numerical computation. The results have been compared with paraxial ray approximation, Gaussian profile of laser beam and only with the relativistic nonlinearity. Numerical results suggest that the focusing of the cosh-Gaussian laser beam, the amplitude of electron plasma wave, and energy gain by electrons increases in non-paraxial region, when relativistic and ponderomotive nonlinearities are simultaneously operative. In addition, it has also been observed that the electron plasma wave is driven more efficiently by a cosh-Gaussian laser beam that accelerates plasma electrons to higher energies.

scholarly journals THz radiation by amplitude-modulated self-focused Gaussian laser beam in ripple density plasma

2015 ◽  
Vol 33 (2) ◽  
pp. 257-263 ◽  
Author(s):  
Subodh Kumar ◽  
Ram Kishor Singh ◽  
Monika Singh ◽  
R. P. Sharma
Keyword(s):  
Laser Beam ◽  
Ponderomotive Force ◽  
Modulation Frequency ◽  
Transverse Component ◽  
Thz Radiation ◽  
Gaussian Laser Beam ◽  
Laser Propagation ◽  
Transverse Current ◽  
Self Focusing ◽  
Density Plasma

AbstractThe effect of self-focusing and defocusing on terahertz (THz) generation by amplitude-modulated Gaussian laser beam in rippled density plasma is investigated. A stronger transient transverse current is generated by transverse component of ponderomotive force exerted by laser on electrons that drives radiation at the modulation frequency (which is chosen to be in the THz domain) because of the variation in intensity in the direction transverse to the laser propagation. Numerical simulations indicate the enhancement of THz yield by many folds due to self-focusing of laser beam in comparison with that without self-focusing. The transient focusing of laser beam and its effect on the generated THz amplitude has also been studied.

scholarly journals Self-Focusing of High-Power Laser Beam Through Cold Uniform Magnetized Plasma

2020 ◽  
Vol 3 (11) ◽  
pp. 137-140
Author(s):  
Sudarshan Kumar Chakravarti
Keyword(s):  
Laser Beam ◽  
Expansion Method ◽  
Spot Size ◽  
Magnetized Plasma ◽  
Intense Laser ◽  
Gaussian Profile ◽  
Self Focusing ◽  
Focusing Property ◽  
Set Up

In present paper the determination of the spot size of an ultra-short laser beam in uniform magnetized plasma with a dominant cold plasma has been studied. The liner dispersion relation of the laser beam propagating in Magnetized plasma have been found. Magnetic field is set up and source dependent expansion method is applied to determining the spot size of the intense laser beam with gaussian profile. The transverse magnetization of plasma and its impact on the self-focusing property of the dense laser governing to reduction in critical power necessary to self-focusing beam is shown.

scholarly journals Stability and dynamics of a cosh-Gaussian laser beam in relativistic thermal quantum plasma

2018 ◽  
Vol 36 (3) ◽  
pp. 341-352 ◽  
Author(s):  
Ranju Mahajan ◽  
Richa ◽  
Tarsem Singh Gill ◽  
Ravinder Kaur ◽  
Munish Aggarwal
Keyword(s):  
Laser Beam ◽  
Phase Modulation ◽  
Variational Approach ◽  
Significant Contribution ◽  
Vital Role ◽  
The Self ◽  
Quantum Plasma ◽  
Propagation Characteristics ◽  
Gaussian Laser Beam ◽  
Self Focusing

AbstractThis paper presents an investigation on the self-focusing of a cosh-Gaussian laser beam in the thermal quantum plasma (TQP) by taking into account the effects of relativistic nonlinearity. An appropriate nonlinear Schrödinger equation has been solved analytically by applying the variational approach. The self-focusing and the self-phase modulation are examined under a variety of parameters. The self-trapping of a cosh-Gaussian laser beam is further studied at various values of the decentered parameter, b with different absorption levels, ${k}^{\prime}_i$. Numerical analysis shows that these parameters play a vital role in propagation characteristics. The significant contribution of the quantum effects to enhance the self-focusing and minimize the longitudinal phase has been observed. Further, a comparison has been made with the classical relativistic (CR), the relativistic cold quantum (RCQ), and the thermal quantum (TQ) regimes. The self-focusing is found to occur earlier and is strongest for the case of TQP in the present analysis.

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