Nonlinear Brillouin amplification of finite-duration seeds in the strong coupling regime

Abstract

Parametric plasma processes received renewed interest in the context of generating ultra-intense and ultra-short laser pulses up to the exawatt-zetawatt regime. Both Raman as well as Brillouin amplifications of seed pulses were proposed. Here, we investigate Brillouin processes in the one-dimensional (1D) backscattering geometry with the help of numerical simulations. For optimal seed amplification, Brillouin scattering is considered in the so called strong coupling (sc) regime. Special emphasis lies on the dependence of the amplification process on the finite duration of the initial seed pulses. First, the standard plane-wave instability predictions are generalized to pulse models, and the changes of initial seed pulse forms due to parametric instabilities are investigated. Three-wave-interaction results are compared to predictions by a new (kinetic) Vlasov code. The calculations are then extended to the nonlinear region with pump depletion. Generation of different seed layers is interpreted by self-similar solutions of the three-wave interaction model. Similar to Raman amplification, shadowing of the rear layers by the leading layers of the seed occurs. The shadowing is more pronounced for initially broad seed pulses. The effect is quantified for Brillouin amplification. Kinetic Vlasov simulations agree with the three-wave interaction predictions and thereby affirm the universal validity of self-similar layer formation during Brillouin seed amplification in the strong coupling regime. V C 2013 AIP Publishing LLC.

Control of Brillouin short-pulse seed amplification by chirping the pump pulse

“…Then, for Brillouin scattering, the transition from weak coupling to strong coupling Brillouin becomes favorable. 17,18 Wave-breaking 19 should be avoided. Analysis of these effects lead for Brillouin seed amplification to the conclusion 15 that plasma density should be sufficiently low since high density implies filamentation.…”

“…6 Using kinetic Vlasov simulations and analytical estimates, the influence of the finite duration of initial seeds on the amplification process was studied in Ref. 17.…”

Relativistic Eulerian Vlasov simulations of the amplification of seed pulses by Brillouin backscattering in plasmas

“…[1][2][3][4][5][6][7][8][9][10][11][12][13][14] In this process, there is an energy transfer, mediated by a resonant plasma wave, through stimulated scattering from a long, high energy, pump electromagnetic wave ðx 0 ;k 0 Þ, to an initially low-intensity ultra-short seed pulse ðx s ;k s Þ. The resonant plasma wave can be either an electron plasma wave ðx pe ;k pe Þ in the stimulated Raman scattering (SRS) process or an ionic wave ðx pi ;k pi Þ in the stimulated Brillouin scattering (SBS) process.…”

“…7 In the present work, we study the SBS amplification in the strong-coupling (sc) regime for counter-propagating pump and seed pulses. 1,5 The potential advantages of the technique have been discussed in several publications (for instance, Refs. 3 and 5).…”

Short-pulse amplification by strongly coupled stimulated Brillouin scattering

“…The differences between SRS and SBS have been articulated with varying degrees of rigor, though direct comparisons appear mostly in literature on SBS, where the following advantages for Brillouin amplification over Raman amplification have been presented: (1) the pump and seed lasers may have almost the same frequency [3,39,45,48,49,57,59], (2) energy loss to the plasma wave, which results from conservation of energy and is described by the Manley-Rowe relations, may be lower for SBS than for SRS, [3,39,46,52], i.e. a greater degree of pump depletion is obtained [45,46,57], (3) SBS is more robust than SRS to plasma inhomogeneities in density or temperature [3,39,45,51], (4) SBS is better suited for producing pulses with high total power or energy, in part because the lower sensitivity to inhomogeneity allows larger diameter plasmas to be used [51], (5) only SBS may be used in the regime 0.25 < N < 1 [52], (6) the duration of a Brillouin-amplified pulse can be shortened to within a factor of 8 of that for a Raman compressed pulse [3], suggesting that the two methods are capable of comparable pulse-compression, (7) a shorter interaction length is required for SBS because the energy transfer is fast [3,45,57], which is sometimes quantified as SRS requiring mm to cm scale plasmas whereas SBS can be conducted in 100 µm [46], and (8) SBS may be viable in regimes where SRS is limited by particle trapping and wavebreaking [3] and can therefore support pump amplitudes several orders of magnitude higher than SRS [59].…”