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

Abstract

Seed amplification via Brillouin backscattering of a long pump pulse is considered. Similar to Raman amplification, several obstructive effects may occur during short-pulse Brillouin amplification. One is the spontaneous Raman backscattering of the pump before interacting with the seed. Preforming the plasma and/or chirping the pump will reduce unwanted pump backscattering. Optimized regions for low-loss pump propagation were proposed already in conjunction with Raman seed amplification. Hence, the influence of the chirp of the pump during Brillouin interaction with the seed becomes important and will be considered here. Both, the linear as well as the nonlinear evolution phases of the seed caused by Brillouin amplification under the action of a chirped pump are investigated. The amplification rate as well as the seed profiles are presented as function of the chirping rate. Also the dependence of superradiant scaling rates on the chirp parameter is discussed. V C 2015 AIP Publishing LLC. [http://dx.

New criteria for efficient Raman and Brillouin amplification of laser beams in plasma

“…We used a long plasma column with constant electron density and plasma frequency (see Refs. 47 , 55 – 57 for a discussion on non-constant plasma densities). For the cold-plasma Raman simulations, we used a plasma density corresponding to , pump laser amplitudes , , , and where , and pump pulse durations up to picoseconds.…”

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

“…At large negative delays, the high intensity part of the pump leaves the plasma before the seed arrival. Interaction occurs in the linear regime with a slow growth rate and the weakly amplified seed becomes longer [24]. This is also the case for intermediate positive delays since the seed mostly interacts with the low intensity rising edge of the pump.…”

“…That was a proof-of-principle experiment, the transition into the selfsimilar regime and its consequences on the amplified seed (pulse duration, frequency spectrum, amplification length) were not studied, nor the Raman and Brillouin interplay. In the following, we report on the first observation of the signatures of the transition from linear to self-similar regimes of SC-SBA, so far only predicted by theory and simulations [13,24]. With a new fully head-on collision geometry, subpicosecond pulses are amplified by a factor of 5 with energy transfers of few tens of mJ.…”

“…This growth is accompanied by a temporal stretching of the pulse. To be efficient, SC-SBA needs to enter the self-similar regime [13,24], where non-negligible energy transfer and pulse compression occur. Other signatures of this regime are a significant and nonsymmetric broadening of the frequency spectrum (in addition to the down-shift in the linear regime), and the amplitude growing as a power law of the amplification length.…”

Boosting the performance of Brillouin amplification at sub-quarter-critical densities via reduction of parasitic Raman scattering

“…In recent years, substantial progress has been made in both experiments [10][11][12][13][14][15][16] and modelling [17][18][19][20][21][22][23][24][25][26] of plasma-based Raman and Brillouin amplification. In order to turn these processes into practical schemes for the production of high-power laser pulses, controlling the quality of the amplified pulse (smooth envelope, low-intensity prepulse) is as important as maximising its power and energy.…”