scholarly journals Nonlinear Mixing of Two Laser Beams and THz Plasmons Generation in Graphene Coated Optical Fibre

2022 ◽  
Author(s):  
Neha Verma ◽  
Anil Govindan ◽  
Pawan Kumar
Keyword(s):  
Optical Fibre ◽  
Laser Intensity ◽  
Ponderomotive Force ◽  
Difference Frequency ◽  
Laser Beams ◽  
Thz Radiation ◽  
Suitable Material ◽  
Radiation Generation ◽  
Nonlinear Mixing ◽  
The Difference

Abstract Graphene is a most suitable material for Terahertz (THz) radiation generation. An efficient mechanism of THz surface plasmons (THz SPs) generation in graphene coated optical fibre by nonlinear mixing of two laser beams is proposed. The graphene coated fiber supports THz SPs with plasmon resonance in the THz regime and controllable by thickness of graphene and radius of optical fibre. The laser beams exert a difference frequency ponderomotive force on the electrons of the graphene. This ponderomotive force induces a nonlinear current in graphene which driving the difference frequency THz SPs. The normalized amplitude of THz SPs decreases with frequency as the nonlinear coupling gets weaker. The efficiency of the device is around 0.01% at a laser intensity of 3x1014 W/cm2. This scheme will be useful making the compact THz radiation source and THz plasmon sensor.

scholarly journals Generation of terahertz radiation by beating of two circular flat-topped laser beams in collisional plasma

2015 ◽  
Vol 33 (4) ◽  
pp. 713-722 ◽  
Author(s):  
Farhad Bakhtiari ◽  
Masoud Yousefi ◽  
Shole Golmohammady ◽  
Seyed Masoud Jazayeri ◽  
Bijan Ghafary
Keyword(s):  
Ponderomotive Force ◽  
Laser Beams ◽  
Thz Radiation ◽  
Incident Laser ◽  
Plasma Parameters ◽  
Steep Gradient ◽  
Highly Sensitive ◽  
Radiation Generation ◽  
Spatially Periodic ◽  
Beating Frequency

AbstractThis paper presents a scheme of terahertz (THz) radiation generation based on beating of two flat-topped laser beams by different frequencies and the same electric field amplitudes in actual plasma with spatially periodic density that electron–neutral collisions have been taken into account. Flat-topped laser beams have the exclusive features such as steep gradient in distribution of laser intensities, wider cross-section in comparison with other profiles, which make stronger ponderomotive force and lead to stronger nonlinear current and hence, THz radiation of higher field. The effects of laser and plasma parameters on THz radiation generation are investigated analytically. It is shown that by increasing the order of flatness of incident laser beams, because of their steep gradient, good enhancement in emitted THz radiation take place. It can be deduced that by increasing beating frequency, efficiency of THz generation decreases which can be compensated by manipulating in density ripple magnitudes. The intensity of the emitted radiations is found to be highly sensitive to the order of flatness. Based on the results of this paper, optimization of laser and plasma parameters can increase the efficiency of THz radiation generation strongly.

scholarly journals Effects of transverse static electric field on terahertz radiation generation by beating of two transversely modulated Gaussian laser beams in a plasma

2014 ◽  
Vol 32 (3) ◽  
pp. 375-381 ◽  
Author(s):  
Prateek Varshnety ◽  
Vivek Sajal ◽  
Prashant Chauhan ◽  
Ravindra Kumar ◽  
Navneet K. Sharma
Keyword(s):  
Electric Field ◽  
Ponderomotive Force ◽  
Beam Width ◽  
Laser Beams ◽  
Thz Radiation ◽  
Gradient Force ◽  
Pressure Gradient Force ◽  
Static Electric Field ◽  
Radiation Generation ◽  
Frequency Laser

AbstractResonant excitation of terahertz (THz) radiation by nonlinear coupling of two filamented spatial-Gaussian laser beams of different frequencies and wave numbers is studied in plasma having transverse static electric field. The static ponderomotive force due to filamented lasers is balanced by the pressure gradient force which gives rise to transverse density ripple, while, the nonlinear ponderomotive force at frequency difference of beating lasers couples with density ripple giving rise to stronger transverse nonlinear current which results into the excitation of THz radiation at resonance. The coupling is further enhanced by the presence of static electric field and spatial-Gaussian nature of laser beams. An increase of six-fold in the normalized amplitude of THz is observed by applying a direct current field of about 50 KV. Effects of frequency, laser beam width, and periodicity factor of modulated laser amplitude are studied for the efficient THz radiation generation. These results can be utilized for generating controlled tunable THz sources for medical applications using low filament intensities (~ 1014 W/cm2) of beating lasers.

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

2018 ◽  
Vol 36 (2) ◽  
pp. 236-245 ◽  
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.

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

2016 ◽  
Vol 34 (4) ◽  
pp. 569-575 ◽  
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.

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

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.

scholarly journals Excitation of terahertz radiation generation by obliquely incident beating lasers on a hot magnetized plasma with step density profile

2017 ◽  
Vol 35 (3) ◽  
pp. 528-533 ◽  
Author(s):  
K.L. Mann ◽  
V. Sajal ◽  
N.K. Sharma
Keyword(s):  
Space Charge ◽  
Density Profile ◽  
Ponderomotive Force ◽  
Magnetized Plasma ◽  
Thz Radiation ◽  
Space Charge Field ◽  
Non Linear ◽  
Radiation Generation ◽  
Step Density ◽  
Charge Field

AbstractA scheme of resonant terahertz (THz) radiation generation by non-linear beating of two lasers in hot magnetized plasma with step density profile is investigated. Beating lasers of frequency difference ω1 − ω2 ≈ ωp(~1 THz) is incident obliquely on plasma surface and exerts non-linear ponderomotive force on plasma electrons. The plasma electrons start oscillating in the plane of incidence and give rise to space charge field to maintain plasma neutrality. In turn, both ponderomotive force and space charge field excites a non-linear surface current, responsible for THz radiation generation on the reflection side. The coupling between plasma wave and electromagnetic wave present (inside the plasma as well as on reflection side) becomes stronger in the presence of the transverse DC magnetic field. THz radiation amplitude is optimized at an angle of incidence θ ~ 50–70°.

Terahertz wave generation by beating of two spatial-Gaussian lasers in collisional plasma

2014 ◽  
Vol 80 (3) ◽  
pp. 453-463 ◽  
Author(s):  
M. Sharifian ◽  
H. R. Sharifinejad ◽  
H. Golbakhsi
Keyword(s):  
Electric Fields ◽  
Transverse Direction ◽  
Ponderomotive Force ◽  
Collision Frequency ◽  
Terahertz Wave ◽  
Wave Generation ◽  
Collisional Plasma ◽  
Laser Beams ◽  
Thz Radiation ◽  
Wave Numbers

This paper revisits the resonant excitation of terahertz (THz) radiation by beating of two spatial-Gaussian laser beams shaving different frequencies and wave numbers but the same electric fields, where the ponderomotive force in the transverse direction is resulted due to the beating and spatial variation of the field of lasers. Effect of the electron-neutral collision frequency on the THz wave generation in the collisional plasma has been discussed.

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

2015 ◽  
Vol 33 (3) ◽  
pp. 519-524 ◽  
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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