Strong terahertz radiation generation by beating of extra-ordinary mode lasers in a rippled density magnetized plasma

AbstractA scheme of terahertz radiation generation is proposed by beating of two extra-ordinary lasers having frequencies and wave numbers$\lpar {\rm \omega}_1\comma \; \vec k_1 \rpar $and$\lpar {\rm \omega}_2\comma \; \vec k_2 \rpar $, respectively in a magnetized plasma. Terahertz wave is resonantly excited at frequency$\lpar {\rm \omega}_1 - {\rm \omega}_2 \rpar $and wave number (k1 − k2 + q) with a wave number mismatch factorqwhich is introduced by the periodicity of plasma density ripples. In this process, the lasers exert a beat ponderomotive force on plasma electrons and impart them an oscillatory velocity with both transverse and longitudinal components in the presence of transverse static magnetic field. The oscillatory velocity couples with density ripples and produces a nonlinear current that resonantly excites the terahertz radiation. Effects of periodicity of density ripples and applied magnetic field are analyzed for strong THz radiation generation. The terahertz radiation generation efficiency is found to be directly proportional to the square of density ripple amplitude and rises with the magnetic field strength. With the optimization of these parameters, the efficiency ~10−3is achieved in the present scheme. The frequency and power of generated THz radiation can be better tuned with the help of parameters like density ripple amplitude, periodicity and applied magnetic field strength in the present scheme.

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

Laser and Particle Beams ◽

10.1017/s0263034619000685 ◽

2019 ◽

Vol 37 (4) ◽

pp. 415-427

Author(s):

Gunjan Purohit ◽

Vinod Rawat ◽

Priyanka Rawat

Keyword(s):

Magnetic Field ◽

Numerical Study ◽

Beat Frequency ◽

Magnetized Plasma ◽

Laser Beams ◽

Thz Radiation ◽

Highly Sensitive ◽

Oscillatory Velocity ◽

Radiation Generation ◽

Paraxial Ray

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.

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Strong terahertz radiation generation by beating of two x-mode spatial triangular lasers in magnetized plasma

Laser and Particle Beams ◽

10.1017/s0263034614000640 ◽

2014 ◽

Vol 33 (1) ◽

pp. 51-58 ◽

Cited By ~ 20

Author(s):

Prateek Varshney ◽

Vivek Sajal ◽

Sweta Baliyan ◽

Navneet K. Sharma ◽

Prashant K. Chauhan ◽

...

Keyword(s):

Magnetic Field ◽

Terahertz Radiation ◽

Beam Width ◽

Laser Pulses ◽

Magnetized Plasma ◽

Thz Radiation ◽

Dc Magnetic Field ◽

Radiation Generation ◽

Transverse And Longitudinal Components ◽

Frequency Laser

AbstractResonant THz radiation generation is proposed by beating of two spatial-triangular laser pulses of different frequencies (ω1, ω2) and wave numbers $\lpar \vec k_1 \comma \; \vec k_2 \rpar $ in plasma having external static magnetic field. Laser pulses co-propagating perpendicular to a dc magnetic field exert a nonlinear ponderomotive force on plasma electrons, imparting them an oscillatory velocity with finite transverse and longitudinal components. Oscillatory plasma electrons couple with periodic density ripples n′ = nq0eiqz to produce a nonlinear current, i.e., responsible for resonantly driving terahertz radiation at $\lpar {\rm \omega} = {\rm \omega} _1 - {\rm \omega} _2 \comma \; \vec k = \vec k_1 - \vec k_2 + \vec q\rpar $. Effects of THz wave frequency, laser beam width, density ripples, and applied magnetic field are studied for the efficient THz radiation generation. The frequency and amplitude of THz radiation were observed to be better tuned by varying dc magnetic field strength and parameters of density ripples (amplitude and periodicity). An efficiency about 0.02 is achieved for laser intensity of 2 × 1015 W/cm2 in a plasma having density ripples about 30%, plasma frequency about 1 THz and magnetic field about 100 kG.

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Tunable terahertz radiation generation by nonlinear photomixing of cosh-Gaussian laser pulses in corrugated magnetized plasma

Laser and Particle Beams ◽

10.1017/s0263034617000167 ◽

2017 ◽

Vol 35 (2) ◽

pp. 279-285 ◽

Cited By ~ 8

Author(s):

P. Varshney ◽

V. Sajal ◽

A. Upadhyay ◽

J. A. Chakera ◽

R. Kumar

Keyword(s):

Magnetic Field ◽

Beam Quality ◽

Beam Width ◽

Laser Pulses ◽

Magnetized Plasma ◽

Thz Radiation ◽

Oscillatory Velocity ◽

Radiation Generation ◽

Factor Α

AbstractThis paper presents a scheme of THz generation by nonlinear photomixing of two cosh-Gaussian lasers pulses having different frequencies (ω1, ω2) and wave numbers $(\vec k_1, \vec k_2 )$ and same electrical field amplitude in a corrugated plasma embedded with transverse static magnetic field. Cosh-Gaussian laser pulses have steep gradient in intensity profile along with wider cross-section, which exerts a stronger nonlinear ponderomotive force at ω1 − ω2 and $\vec k_1 - \vec k_2 $ on plasma electrons imparting a nonlinear oscillatory velocity to plasma electrons. Oscillatory plasma electrons couple with the density ripple n′ = nα0eiαx to produce a nonlinear current, which is responsible for resonant THz radiation at frequency $\sim\left( {{\rm \omega} _{\rm c}^2 + {\rm \omega} _{\rm p}^2} \right)^{1/2} $. The amplitude, efficiency and beam quality of THz radiation can be optimized by choosing proper corrugation factor (α of the plasma), applied magnetic field (ωc), decentered parameter (b), and beam width parameter a0 of cosh-Gaussian lasers. An efficiency of $\sim\!10^{ - 2} - 10^{ - 1} $ is achieved for laser electric field E = 3.2 × 109 V/cm.

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Strong terahertz radiation generation by cosh-Gaussian laser beams in axially magnetized collisional plasma under non-relativistic ponderomotive regime

Laser and Particle Beams ◽

10.1017/s0263034618000216 ◽

2018 ◽

Vol 36 (2) ◽

pp. 236-245 ◽

Cited By ~ 4

Author(s):

Prateek Varshney ◽

Ajit Upadhayay ◽

K. Madhubabu ◽

Vivek Sajal ◽

J. A. Chakera

Keyword(s):

Magnetic Field ◽

Ponderomotive Force ◽

Beat Frequency ◽

Magnetized Plasma ◽

Laser Beams ◽

Thz Radiation ◽

Thz Wave ◽

Oscillatory Velocity ◽

Non Linear ◽

Radiation Generation

AbstractWe propose a scheme for terahertz (THz) radiation generation by non-linear mixing of two cosh-Gaussian laser beams in axially magnetized plasma with spatially periodic density ripple where electron-neutral collisions have been taken into account. The laser beams exert a non-linear ponderomotive force due to spatial non-uniformity in the intensity. The plasma electrons acquire non-linear oscillatory velocity under the influence of ponderomotive force. This oscillatory velocity couples with preformed density ripples (n′ = n0αeiαz) to generate a strong transient non-linear current that resonantly derives THz radiation of frequency ~ωh (upper hybrid frequency). Laser frequencies (ω1 and ω2) are chosen such that the beat frequency (ω) lies in the THz region. The periodicity of density ripple provides phase-matching conditions (ω = ω1 − ω2 and $\vec k = \vec k_1 - \vec k_2 + {\rm \vec \alpha} $) to transfer maximum momentum from laser to THz radiation. The axially applied external magnetic field can be utilized to enhance the non-linear coupling and control various parameters of generated THz wave. The effects of decentered parameters (b), collisional frequency (νen), and magnetic field strength (B0 = ωcm/e) are analyzed for strong THz radiation generation. Analytical results show that the amplitude of THz wave enhances with decentered parameters as well as with the magnitude of axially applied magnetic field. The THz amplitude is found to be highly sensitive to collision frequency.

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

Laser and Particle Beams ◽

10.1017/s0263034615000865 ◽

2015 ◽

Vol 33 (4) ◽

pp. 741-747 ◽

Cited By ~ 2

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.

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Enhanced terahertz radiation generation by two-color laser pulses propagating in plasma

Laser and Particle Beams ◽

10.1017/s0263034616000173 ◽

2016 ◽

Vol 34 (2) ◽

pp. 378-383 ◽

Cited By ~ 1

Author(s):

N.K. Verma ◽

P. Jha

Keyword(s):

Magnetic Field ◽

External Magnetic Field ◽

Numerical Model ◽

Laser Pulses ◽

Magnetized Plasma ◽

Thz Radiation ◽

Homogeneous Plasma ◽

One Dimensional ◽

Radiation Generation ◽

Transverse Electromagnetic

AbstractA one-dimensional (1D) numerical model for studying enhanced terahertz (THz) radiation generation by mixing of ordinary and extraordinary modes of two-color laser pulses propagating in magnetized plasma has been presented. The direction of the static external magnetic field is such that one of the two laser pulses propagates in the extraordinary mode, while the other pulse propagates in the ordinary mode, through homogeneous plasma. A transverse electromagnetic wave with frequency in the THz range is generated due to the presence of the external magnetic field. It is observed that larger amplitude THz radiation can be generated by mixing of the ordinary and extraordinary modes of the two-color laser pulses as compared with the single laser pulse propagating in the extraordinary mode. Further, 2D simulations using the XOOPIC code show that the fields obtained via simulation study are compatible with those obtained from the numerical model.

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Generation of terahertz radiation by beating of two laser beams in collisional magnetized plasma

Laser and Particle Beams ◽

10.1017/s0263034616000513 ◽

2016 ◽

Vol 34 (4) ◽

pp. 569-575 ◽

Cited By ~ 5

Author(s):

A. Hematizadeh ◽

S.M. Jazayeri ◽

B. Ghafary

Keyword(s):

Magnetic Field ◽

Magnetized Plasma ◽

Laser Beams ◽

Thz Radiation ◽

Plasma Parameters ◽

Circularly Polarized ◽

Left Hand ◽

Polarized Waves ◽

Radiation Generation ◽

The Magnetic Field

AbstractThis paper presents analytical calculations for terahertz (THz) radiation by beating of two cosh-Gaussian laser beams in a density rippled collisional magnetized plasma. Lasers beams exert a ponderomotive force on the electrons of plasma in beating frequency which generates THz waves. The magnetic field was considered parallel to the direction of lasers which leads to propagate right-hand circularly polarized or left-hand circularly polarized waves in the plasma depending on the phase matching conditions. Effects of collision frequency, decentered parameter of lasers and the magnetic field strength are analyzed for THz radiation generation. By the optimization of laser and plasma parameters, the efficiency of order 27% can be achieved.

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High-intensity terahertz generation by nonlinear frequency-mixing of lasers in plasma with DC magnetic field

Laser and Particle Beams ◽

10.1017/s0263034615000609 ◽

2015 ◽

Vol 33 (3) ◽

pp. 519-524 ◽

Cited By ~ 16

Author(s):

Anil K. Malik ◽

Kunwar Pal Singh

Keyword(s):

Magnetic Field ◽

High Intensity ◽

Ponderomotive Force ◽

Wave Number ◽

Thz Radiation ◽

Nonlinear Frequency ◽

External Static Magnetic Field ◽

Radiation Generation ◽

Tunable Frequency ◽

Frequency Mixing

AbstractWe propose a mechanism of highly focused, tunable and high-intensity terahertz (THz) radiation generation by frequency-mixing of two super-Gaussian lasers with frequencies ω1, ω2 and wave numbers k1, k2 (laser profile index p > 2) in a corrugated plasma in the presence of external static magnetic field ${B_0}\hat z$. In this process, a strong nonlinear ponderomotive force is offered to the plasma electrons at frequency ω′ = ω1 − ω2 and wave number k′ = k1 − k2 by laser beams. The ponderomotive force results in a strong, controllable nonlinear transverse oscillatory current, which can be optimized by optimizing the external magnetic field, ripple parameters, and laser indexes. This controllable current produces focused and intense THz radiation of tunable frequency and power along with a remarkable efficiency ~25%.

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