title: Signatures of the Self-Similar Regime of Strongly Coupled Stimulated Brillouin Scattering for Efficient Short Laser Pulse Amplification.
abstract: Plasma-based laser amplification is considered as a possible way to overcome the technological limits of present day laser systems and achieve exawatt laser pulses. Efficient amplification of a picosecond laser pulse by stimulated Brillouin scattering (SBS) of a pump pulse in a plasma requires to reach the self-similar regime of the strongly coupled (SC) SBS. In this Letter, we report on the first observation of the signatures of the transition from linear to self-similar regimes of SC-SBS, so far only predicted by theory and simulations. 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. We observe pulse shortening, frequency spectrum broadening, and down-shifting for increasing gain, signatures of SC-SBS amplification entering the self-similar regime. This is also confirmed by the power law dependence of the gain on the amplification length: doubling the interaction length increases the gain by a factor 1.4. Pump backward Raman scattering (BRS) on SC-SBS amplification has been measured for the first time, showing a strong decrease of the BRS amplitude and frequency bandwidth when SBS seed amplification occurs.
authors.affiliation: Dipartimento SBAI, Università di Roma "La Sapienza," Via Antonio Scarpa 14, 00161 Rome, Italy.|INFN-Sezione Roma 1-SAPIENZA, University of Rome, 00185 Rome, Italy.
authors.forename: L
authors.initials: L
authors.lastname: Lancia
authors.affiliation: Dipartimento SBAI, Università di Roma "La Sapienza," Via Antonio Scarpa 14, 00161 Rome, Italy.|INFN-Sezione Roma 1-SAPIENZA, University of Rome, 00185 Rome, Italy.
authors.forename: A
authors.initials: A
authors.lastname: Giribono
authors.affiliation: Dipartimento SBAI, Università di Roma "La Sapienza," Via Antonio Scarpa 14, 00161 Rome, Italy.|LULI-CNRS, École Polytechnique, CEA: Université Paris-Saclay; UPMC Université Paris 06: Sorbonne Universités, F-91128 Palaiseau cedex, France.
authors.forename: L
authors.initials: L
authors.lastname: Vassura
authors.affiliation: LULI-UPMC Université Paris 06: Sorbonne Universités; CNRS, Ecole Polytechnique, CEA: Université Paris-Saclay, F-75252 Paris cedex 05, France.
authors.forename: M
authors.initials: M
authors.lastname: Chiaramello
authors.affiliation: LULI-UPMC Université Paris 06: Sorbonne Universités; CNRS, Ecole Polytechnique, CEA: Université Paris-Saclay, F-75252 Paris cedex 05, France.
authors.forename: C
authors.initials: C
authors.lastname: Riconda
authors.affiliation: Institute of Physics of the ASCR, ELI-Beamlines, 18221 Prague, Czech Republic.
authors.forename: S
authors.initials: S
authors.lastname: Weber
authors.affiliation: LULI-CEA, CNRS, École Polytechnique: Université Paris-Saclay; UPMC Université Paris 06: Sorbonne Universités, F-91128 Palaiseau cedex, France.
authors.forename: A
authors.initials: A
authors.lastname: Castan
authors.affiliation: LULI-CNRS, École Polytechnique, CEA: Université Paris-Saclay; UPMC Université Paris 06: Sorbonne Universités, F-91128 Palaiseau cedex, France.
authors.forename: A
authors.initials: A
authors.lastname: Chatelain
authors.affiliation: GSI Helmholtzzentrum für Schwerionenforschung GmbH, 64291 Darmstadt, Germany.
authors.forename: A
authors.initials: A
authors.lastname: Frank
authors.affiliation: LULI-CEA, CNRS, École Polytechnique: Université Paris-Saclay; UPMC Université Paris 06: Sorbonne Universités, F-91128 Palaiseau cedex, France.|ILPP, Heinrich-Heine Universität Düsseldorf, 40225 Düsseldorf, Germany.
authors.forename: T
authors.initials: T
authors.lastname: Gangolf
authors.affiliation: IZEST, CEA, École Polytechnique, F-91128 Palaiseau cedex, France.
authors.forename: M N
authors.initials: MN
authors.lastname: Quinn
authors.affiliation: LULI-CNRS, École Polytechnique, CEA: Université Paris-Saclay; UPMC Université Paris 06: Sorbonne Universités, F-91128 Palaiseau cedex, France.
authors.forename: J
authors.initials: J
authors.lastname: Fuchs
authors.affiliation: LULI-CNRS, École Polytechnique, CEA: Université Paris-Saclay; UPMC Université Paris 06: Sorbonne Universités, F-91128 Palaiseau cedex, France.
authors.forename: J-R
authors.initials: JR
authors.lastname: Marquès