The efficiency of Raman amplification in the wavebreaking regime

Edwards, Matthew R.; Toroker, Z.; Mikhailova, Julia M.; Fisch, Nathaniel J.

doi:10.1063/1.4926514

Cited by 41 publications

(24 citation statements)

References 43 publications

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“…Previous theoretical and computational works have focussed on the optimal pump amplitude for efficient amplification [2,5,11,12]. Although it is known that the highest efficiencies are achieved below the wavebreaking threshold, the necessarily low intensities would require large interaction volumes to scale to high power.…”

Section: Introductionmentioning

confidence: 99%

Raman amplification in the coherent wave-breaking regime

Farmer¹,

Pukhov²

2015

Phys. Rev. E

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In regimes far beyond the wavebreaking threshold of Raman amplification, we show that significant amplifcation can occur after the onset of wavebreaking, before phase mixing destroys the coherent coupling between pump, probe and plasma wave. Amplification in this regime is therefore a transient effect, with the higher-efficiency "coherent wavebreaking" (CWB) regime accessed by using a short, intense probe. Parameter scans illustrate the marked difference in behaviour between below wavebreaking, in which the energy-transfer efficiency is high but total energy transfer is low, wavebreaking, in which efficiency is low, and CWB, in which moderate efficiencies allow the highest total energy transfer.

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Section: Introductionmentioning

confidence: 99%

Raman amplification in the coherent wave-breaking regime

Farmer¹,

Pukhov²

2015

Phys. Rev. E

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“…As predicted, there are no secondary trailing peaks. Although, suppression of these peaks is also possible when the pump exceeds the threshold wavebreaking intensity [35][36][37][38][39] , here this was only true for the first 20% of the propagation. We therefore attribute the suppression to the divergence of the pulse, rather than premature breaking of the plasma wave.…”

Section: Resultsmentioning

confidence: 97%

Advantages to a diverging Raman amplifier

Sadler¹,

Silva²,

Fonseca³

et al. 2018

Commun Phys

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The plasma Raman instability can efficiently compress a nanosecond long high-power laser pulse to sub-picosecond duration. Although, many authors envisaged a converging beam geometry for Raman amplification, here we propose the exact opposite geometry; the amplification should start at the intense focus of the seed. We generalise the coupled laser envelope equations to include this non-collimated case. The new geometry completely eradicates the usual trailing secondary peaks of the output pulse, which typically lower the efficiency by half. It also reduces, by orders of magnitude, the initial seed pulse energy required for efficient operation. As in the collimated case, the evolution is self similar, although the temporal pulse envelope is different. A two-dimensional particle-in-cell simulation demonstrates efficient amplification of a diverging seed with only 0.3 mJ energy. The pulse has no secondary peaks and almost constant intensity as it amplifies and diverges.

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“…Next, we adopt a universal model [15] by transforming to the dimensionless variables τ = σRV For constant pump, I a = I 0 , the total pump fluence that was invested in the system, w a = I 0 ∆t a , where ∆t a = 2L/c is the pump duration, can be written as Then, the efficiency can be defined as [38] …”

Section: Discussionmentioning

confidence: 99%

Beyond nonlinear saturation of backward Raman amplifiers

et al. 2016

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Backward Raman amplification is limited by relativistic nonlinear dephasing resulting in saturation of the leading spike of the amplified pulse. Pump detuning is employed to mitigate the relativistic phase mismatch and to overcome the associated saturation. The amplified pulse can then be reshaped into a mono-spike pulse with little precursory power ahead of it, with the maximum intensity increasing by a factor of two. This detuning can be employed advantageously both in regimes where the group velocity dispersion is unimportant and where the dispersion is important but small.

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The efficiency of Raman amplification in the wavebreaking regime

Cited by 41 publications

References 43 publications

Raman amplification in the coherent wave-breaking regime

Raman amplification in the coherent wave-breaking regime

Advantages to a diverging Raman amplifier

Beyond nonlinear saturation of backward Raman amplifiers

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