Signatures of the Self-Similar Regime of Strongly Coupled Stimulated Brillouin Scattering for Efficient Short Laser Pulse Amplification

Abstract

PRL 116, 075001 (2016) PHYSICAL REVIEW LETTERS week ending 19 FEBRUARY 2016 0031-9007=16=116 (7)=075001 (5) 075001-1

Short-pulse amplification by strongly coupled stimulated Brillouin scattering

“…Other works have considered relativistic [44], thermal [58], and collisional [50] effects, as well as the role of instabilities like forward Raman scattering (FRS) [51] on the amplification process. SBS has been demonstrated experimentally [43,52,59], with recently published work suggesting amplification in the self-similar regime, where depletion of the pump beam is significant [59].…”

“…Currently, experimentally demonstrated performance of Raman amplifiers [30] exceeds that of Brillouin amplifiers [43,59] in energy transfer efficiency and peak amplified seed intensity, though higher total energy transfer between pump and seed has been achieved with SBS [59].…”

“…The superradiant threshold depends on the product a seed apump, so the threshold will move for different ratios of seed to pump strength. For experimental work [43,52,59] the full range of tested densities is marked by a line.…”

“…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].…”

“…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]. Additionally, we make the argument (9) that SBS may be appropriate in regimes where Langmuir waves would be collisionally damped.…”