Laser intensity profile based terahertz field enhancement from a mixture of nano-particles embedded in a gas

Varshney, Prateek; Singh, Amit Pratap; Kundu, M.; Gopal, K.

doi:10.1007/s11082-022-03597-9

Cited by 12 publications

(6 citation statements)

References 29 publications

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“…Also, the present physical model reports the enhanced THz field with previously reported studies of the THz field generation in semiconductor plasmas [38] and the mixture of nanoparticles and argon gas. [35] Figure 3 depicts the variation of the normalized terahertz field amplitude with normalized transverse distance for different FG-indices ( f ) of lasers. One can see obvious results of significant enhancement in terahertz field for f = 4, showing subsequently decays for lower values of " f ", i.e., large values of FG-index ( f ) corresponding to the flat top lasers provide better enhancement than lower flat index parameter which is more alike Gaussian pulse.…”

Section: Resultsmentioning

confidence: 99%

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Nonlinear mixing-based terahertz emission in inclined rippled density plasmas

2023

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We propose to investigate the THz field generation using nonlinear mixing mechanism of laser beat wave with inclined rippled density plasmas. Two laser pulses with frequencies (ω 1, ω 2) and wave vectors (κ 1,κ 2) co-propagate and resultant laser beat wave forms at beat frequency (ω 1-ω 2). Laser beat wave imparts a nonlinear force on the ambient electrons and pushes them outward with nonlinear velocity v NL . Coupling of induced density perturbation and nonlinear velocityv NL generates nonlinear currents at laser beat frequency that further generates electromagnetic field E (ω 1-ω 2) in terahertz (THz) range. In present scheme, density ripples are introduced at an angle with respect to laser propagation and flat Gaussian index (f) is introduced in laser field profile that transform curved top of Gaussian field envelope into flat top field envelope. The combined effect of flat laser pulses with inclined density ripples in plasmas shows 10 fold enhancement in THz field amplitude when flat-Gaussian index (f) varies from 1 to 4. Also, THz field intensifies when density ripples inclination increases upto a certain angle and then decreases.

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Section: Resultsmentioning

confidence: 99%

“…The THz field generated by nonlinear mixing mechanism can be estimated from the Maxwell wave equations that are derived from the third and fourth Maxwell's equations, [35] ∇…”

Section: Physical Modelmentioning

confidence: 99%

Nonlinear mixing-based terahertz emission in inclined rippled density plasmas

2023

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“…Herein, we consider a mixture of NPs, consisting of SNPs and CNPs placed in argon gas [29]. Two circularly symmetric Gaussian laser beams are simultaneously propagating through the array of NPs along the z-direction such that their electric field amplitudes vary in the xy-plane.…”

Section: Ponderomotive Force Due To Laser-metal Interactionmentioning

confidence: 99%

“…Javan and Erdi [28] presented a model for the generation of THz radiation via the beat-wave mechanism using Gaussian laser beams in a spatially modulated medium of graphite SNPs and CNPs. Varshney et al [29], Punia et al [30] and Sharma et al [31] independently studied shape-dependent THz radiation using graphite SNPs and CNPs, and concluded that THz emission for CNPs is much greater than that of SNPs, and the mixture of the two NPs further generated higher THz fields. Malik and Punia [32] observed similar results when employing an external periodic electric field on the medium of graphite SNPs and CNPs.…”

Section: Introductionmentioning

confidence: 99%

Magnetic field enhanced terahertz generation from shape-dependent metallic nanoparticles

Simon,

Chauhan

2024

J. Opt.

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This communication deals with the analytical study of terahertz (THz) generation via frequency-difference mechanism using two circularly symmetric Gaussian laser beams with slightly different frequencies ω1 and ω2 and wave vectors k1 and k2 simultaneously propagating through a mixture of spatially corrugated noble-metal nanoparticles. The mixture, consisting of spherical and cylindrical nanoparticles, is placed in a host medium under the influence of an externally applied static magnetic field. The two co-propagating laser beams impart a nonlinear ponderomotive force on electrons of the nanoparticles, causing them to experience nonlinear oscillatory velocity. Further, the consequent nonlinear current density excites terahertz radiation at the beat frequency (=ω1 - ω2). Magnetic field inﬂuences the surface plasmon resonance condition associated with electrons of the nanoparticles due to enhancement in ponderomotive nonlinearities, thereby causing an increment in the amplitude of generated THz field. It is observed that the generated THz radiation has a strong dependence on the shape and size of the nanoparticles in addition to the magnetic field strength. Cylindrical nanoparticles provide greater THz amplitude than spherical nanoparticles due to additional resonance modes, and combining both kinds of nanostructures further enhance the amplitude. THz radiations play an important role in biomedical and pharmaceutical fields, communications, security and THz spectroscopy.

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“…The nonlinear oscillatory velocity couples with preformed ripple 𝑛 ′ = 𝑛 𝛽 𝑒 𝑖𝛽𝑧 Considering both geometries of the NPs, nonlinear macroscopic current density can be written as [41] 𝑗 𝜔 𝑁𝐿 = −(𝛼 𝑠 * 𝑓 𝑠 + 𝛼 𝑐 * 𝑓 𝑐 )𝑛′𝑒𝑣 𝜔 𝑁𝐿 (6) where 𝛼 𝑠 and 𝛼 𝑐 are the arbitrary constants considered to include the individual contribution of spherical and cylindrical nanoparticles, respectively. In the absence of SNPs, 𝛼 𝑠 = 0, 𝛼 𝑐 = 1 and in the absence of CNPs, 𝛼 𝑠 = 1, 𝛼 𝑐 = 0 , while 𝛼 𝑠 = 𝛼 𝑐 = 1 in the medium containing both types of the NPs.…”

Section: Nonlinear Current Density and Thz Radiationmentioning

confidence: 99%

Excitation of tunable terahertz radiation from a mixture of nanoparticles in static magnetic field

Simon,

Chauhan

2023

Preprint

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This communication deals with the analytical study of terahertz (THz) generation via beat-wave mechanism of two circularly symmetric Gaussian laser beams with frequencies \({\omega }_{1}\) and \({\omega }_{2}\) and wave vectors \({\overrightarrow{k}}_{1}\) and \({\overrightarrow{k}}_{2}\)simultaneously propagating through a mixture of spatially corrugated noble-metal nanoparticles (NPs). The mixture, consisting of spherical and cylindrical nanoparticles, is placed in argon gas under the influence of a static magnetic field. The two co-propagating laser beams impart a nonlinear ponderomotive force on electrons of the NPs, causing them to experience nonlinear oscillatory velocity. Further, the consequent nonlinear current density excites terahertz radiation at the beat frequency \(\omega (={\omega }_{1}-{\omega }_{2})\). Magnetic field influences the surface plasmon resonance condition associated with electrons of the nanoparticles due to enhancement in ponderomotive nonlinearities, thereby causing an increment in the amplitude of generated THz field. It is observed that the generated THz radiation has a strong dependence on the shape and size of the NPs in addition to the magnetic field strength. Cylindrical nanoparticles provide greater THz amplitude than spherical nanoparticles due to additional resonance modes, and combining both kinds of nanostructures further enhance the amplitude. THz radiations play an important role in biomedical and pharmaceutical fields, communications, security and THz spectroscopy.

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Laser intensity profile based terahertz field enhancement from a mixture of nano-particles embedded in a gas

Cited by 12 publications

References 29 publications

Nonlinear mixing-based terahertz emission in inclined rippled density plasmas

Nonlinear mixing-based terahertz emission in inclined rippled density plasmas

Magnetic field enhanced terahertz generation from shape-dependent metallic nanoparticles

Excitation of tunable terahertz radiation from a mixture of nanoparticles in static magnetic field

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