Amplification of a seed pumped by a chirped laser in the strong coupling Brillouin regime

Seed amplification via Brillouin backscattering of a long pump laser-pulse is considered. The interaction takes place in the so called strong coupling regime. Pump chirping is applied to mitigate spontaneous Raman backscattering of the pump before interacting with the seed. The strong coupling regim...

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Bibliographic Details
Published in:Physics of plasmas 2015-09, Vol.22 (9)
Main Authors: Schluck, F., Lehmann, G., Spatschek, K. H.
Format: Article
Language:English
Subjects:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY
AMPLIFICATION
AMPLITUDES
BACKSCATTERING
BRILLOUIN EFFECT
Chirp
Coupling
Dependence
LASER RADIATION
Lasers
NONLINEAR PROBLEMS
Plasma physics
PULSES
RAMAN EFFECT
Seeds
STRONG-COUPLING MODEL
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Summary:Seed amplification via Brillouin backscattering of a long pump laser-pulse is considered. The interaction takes place in the so called strong coupling regime. Pump chirping is applied to mitigate spontaneous Raman backscattering of the pump before interacting with the seed. The strong coupling regime facilitates stronger exponential growth and narrower seeds compared to the so called weak coupling regime, although in the latter the scaling with pump amplitude is stronger. Strong coupling is achieved when the pump laser amplitude exceeds a certain threshold. It is shown how the chirp influences both the linear as well as the nonlinear amplification process. First, linear amplification as well as the seed profiles are determined in dependence of the chirping rate. In contrast to the weak coupling situation, the evolution is not symmetric with respect to the sign of the chirping rate. In the nonlinear stage of the amplification, we find an intrinsic chirp of the seed pulse even for an un-chirped pump. We show that chirping the pump may have a strong influence on the shape of the seed in the nonlinear amplification phase. Also, the influence of pump chirp on the efficiency of Brillouin seed amplification is discussed.
ISSN:1070-664X
1089-7674
DOI:10.1063/1.4929859