scholarly journals Efficient THz Generation by Nonlinear Interaction of Gaussian Laser Beam With the Anharmonic and Rippled CNTs Aligned Vertically in the Array

2021 ◽  
Author(s):  
Sandeep Kumar ◽  
Shivani Vij ◽  
Niti Kant ◽  
Vishal Thakur
Keyword(s):  
Magnetic Field ◽  
Carbon Nanotubes ◽  
Laser Beam ◽  
Static Magnetic Field ◽  
Nonlinear Interaction ◽  
Transverse Velocity ◽  
Dielectric Surface ◽  
Thz Radiation ◽  
Gaussian Laser Beam ◽  
Vertically Aligned

Abstract We purpose a theoretical analysis for the generation of efficient terahertz (THz) radiation by using the nonlinear interaction of Gaussian laser beam with vertically aligned anharmonic, and rippled carbon nanotubes (CNTs) array. This array of vertically aligned carbon nanotubes (VA-CNTs) is embedded on the base of the dielectric surface. The VA-CNTs have been magnetized by applying a static magnetic field mutually perpendicular to the direction of propagation of the Gaussian beam and length of CNTs. The Gaussian laser beam passing through the CNTs exerts a nonlinear ponderomotive force on the electrons of CNTs and provides them resonant nonlinear transverse velocity. This produces the nonlinear current which is further responsible for the generation of THz radiation. The anharmonicity plays a vital role in the efficient generation of THz radiation. The anharmonicity arises due to the nonlinear variation of restoration force on the various electrons of CNTs. This anharmonicity in the electrons of CNTs helps in broadening the resonance peak. We have observed that externally applied static magnetic field 110 kg to 330 kg) also paves the way for the enhancement of the normalized THz amplitude.

scholarly journals Interaction of high power laser beam with magnetized plasma and THz generation

2010 ◽  
Vol 28 (4) ◽  
pp. 531-537 ◽  
Author(s):  
R.P. Sharma ◽  
A. Monika ◽  
P. Sharma ◽  
P. Chauhan ◽  
A. Ji
Keyword(s):  
Magnetic Field ◽  
Laser Beam ◽  
High Power ◽  
Nonlinear Interaction ◽  
Difference Frequency ◽  
Thz Radiation ◽  
High Power Laser ◽  
Power Laser ◽  
Circularly Polarized ◽  
Paraxial Ray

AbstractThis paper presents an investigation of the excitation of a Tera hertz (THz) radiation by nonlinear interaction of a circularly polarized high power laser beam and density ripple in collisionless magneto plasma. The ponderomotive force due to the nonlinear interaction between the laser and density ripple generates a nonlinear current at a difference frequency. If the appropriate phase matching conditions are satisfied and the frequency of the ripple is appropriate, then this difference frequency can be brought in the THz range. Filamentation (self focusing) of a circularly polarized beam propagating along the direction of ambient magnetic field in plasma is first investigated within paraxial ray approximation. The beam gets focused when the initial power of the laser beam is greater than its critical power. Resulting localized beam couples with the pre-existing density ripple to produce a nonlinear current driving the THz radiation. Analytical expressions for the beam width of the laser beam, electric vector of the THz wave have been obtained. By changing the strength of the magnetic field, one can enhance or suppress the THz emission. For typical laser beam and plasma parameters with the incident laser power flux = 1014 W/cm2, laser beam radius (r0) = 40 µm, laser frequency (ω0) = 1014 rad/s and plasma density (n0) = 3 × 1018 cm−3, normalized ripple density amplitude (μ) = 0.3, the produced THz emission can be at the level of Giga watt in power.

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.

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 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.

scholarly journals Excitation of an upper hybrid wave by a high power laser beam in plasma

2008 ◽  
Vol 26 (1) ◽  
pp. 61-68 ◽  
Author(s):  
G. Purohit ◽  
P.K. Chauhan ◽  
R.P. Sharma
Keyword(s):  
Magnetic Field ◽  
Laser Beam ◽  
Static Magnetic Field ◽  
Electron Concentration ◽  
Pump Laser ◽  
Electron Mass ◽  
Nonlinear Coupling ◽  
Hybrid Wave ◽  
Power Laser ◽  
Self Focusing

AbstractIn the present investigation, the excitation of an upper hybrid wave (UHW) in a hot collisionless magneto-plasma by a relativistic laser beam propagating perpendicular to the static magnetic field and having its electric vector polarized along the direction of the static magnetic field (ordinary mode) is presented. Due to nonuniform intensity distribution of pump laser, the background electron concentration is modified. The amplitude of the UHW, which depends on the background electron concentration, is thus nonlinearly coupled with the laser beam. The effect of nonlinear coupling between the pump laser and UHW is studied. The effect of the relativistic electron mass nonlinearity and the relativistic self-focusing of the pump laser on the excitation of the UHW have been incorporated. The dynamics of the excitation of the UHW in different power domains of the laser beam is accordingly modified. It has been seen that the effect of changing the strength of the static magnetic field on the nonlinear coupling and the dynamics of the excitation of the UHW is significant. The focusing behavior of the UHW may find its relevance in the heating of plasmas near the upper hybrid resonance.

scholarly journals Relativistic self-focusing and self-phase modulation of cosh-Gaussian laser beam in magnetoplasma

2011 ◽  
Vol 29 (2) ◽  
pp. 183-191 ◽  
Author(s):  
Tarsem Singh Gill ◽  
Ravinder Kaur ◽  
Ranju Mahajan
Keyword(s):  
Magnetic Field ◽  
Laser Beam ◽  
Field Distribution ◽  
Phase Modulation ◽  
Variational Approach ◽  
Beam Width ◽  
Propagation Characteristics ◽  
Gaussian Laser Beam ◽  
Self Phase Modulation ◽  
Self Focusing

AbstractIn this paper, we have investigated the propagation characteristics of cosh-Gaussian laser beam in magnetoplasma using relativistic nonlinearity. The field distribution in the medium is expressed in terms of beam width parameter an and decentred parameter b. An appropriate nonlinear Schräodinger equation has been solved analytically using variational approach. The behaviour of beam width parameter with dimensionless distance of propagation ξ for various b values is examined. Self-phase modulation and self-trapping is also studied under variety of parameters. Further, the effect of magnetic field on self-focusing of the beam have been explored.

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