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Two color laser self focusing and terahertz generation in multi-ion species plasma

Title
Two color laser self focusing and terahertz generation in multi-ion species plasma
Authors
Ahmad, N.Mahmoud, S.T.Purohit, G.Khan, Firoz
Issue Date
2018-04
Citation
Optik, 158, 1533-1542
Type
Article
Article Type
Article
Keywords
Beam plasma interactionsConversion efficiencyEfficiencyElectromagnetic wave emissionFocusingIonsLaser beamsLaser produced plasmasPhase matchingPlasma interactionsTerahertz wavesCo-propagating lasersCumulative effectsLaser-plasma interactionsPonderomotive forcesPower conversion efficienciesTerahertz generationTerahertz radiationTerahertz radiation generationsLight propagation
ISSN
0030-4026
Abstract
An analytical formalism of self focusing of two co-propagating laser beams, fundamental ω1 and close to second harmonic ω2≈2ω1, in a multi-ion species plasma and resonant terahertz radiation generation has been developed. The nonlinearity arises due to ponderomotive force on electrons by both the beams and subsequent ambipolar redistribution of the plasma. The ions of higher charged state are strongly depleted from the axial region due to space charge field effects and electron charge is largely compensated by the ions of lower charge. When the power of the strong beam equals the critical power for its self-guiding, the plasma provides an oscillatory waveguide for the weak beam; the weak beam shrinks and rebounds when its frequency is lower than that of the strong beam, and it swallows and rebounds when the frequency is higher. When both beams are strong the nonlinearities have cumulative effect on both the beams. The cross coupling of the beams gives rise to nonlinear current giving rise to terahertz radiation at ω=ω2−2ω1 frequency. An axial density ripple aids phase matching and gives rise to higher power conversion efficiency. Self focusing leads to enhancement in conversion efficiency. © 2017 Elsevier GmbH
URI
http://hdl.handle.net/20.500.11750/5881
DOI
10.1016/j.ijleo.2017.12.152
Publisher
Elsevier B.V.
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