title: Experimental Evidence of Backward Raman Scattering Driven Cooperatively by Two Picosecond Laser Pulses Propagating Side by Side.
abstract: This Letter investigates experimentally the backward stimulated Raman scattering (SRS) of two copropagating, 1-μm wavelength, 1.5-ps duration laser pulses focused side by side, but not simultaneously, in a preformed underdense plasma. When the two lasers do not interact, one of the pulses (so-called strong) yields a large SRS reflectivity, while the other weak pulse is essentially ineffective as regards SRS. By contrast, the weak pulse shows significant SRS activity if it is launched in the plasma slightly after the strong one, and for time delays as large as about 15 ps. For crossed polarizations and a lateral distance of 80-90  μm, the time delay has to be larger than 3-4 ps for the weak pulse to be active, while it has just to be positive when the polarizations are parallel. The experimental results are discussed with the help of large-scale particle-in-cell simulations.
authors.affiliation: CEA, DAM, DIF, F-91297 Arpajon, France.
authors.forename: C
authors.initials: C
authors.lastname: Rousseaux
authors.affiliation: CEA, DAM, DIF, F-91297 Arpajon, France.
authors.forename: K
authors.initials: K
authors.lastname: Glize
authors.affiliation: LULI-CNRS, Ecole Polytechnique, CEA, Université Paris-Saclay, UPMC Université Paris 06, Sorbonne Universités, F-91128 Palaiseau cedex, France.
authors.forename: S D
authors.initials: SD
authors.lastname: Baton
authors.affiliation: Dipartimento SBAI, Universitá di Roma "La Sapienza," Via Scarpa 14-16, 00161 Roma, Italy.
authors.forename: L
authors.initials: L
authors.lastname: Lancia
authors.affiliation: CEA, DAM, DIF, F-91297 Arpajon, France.
authors.forename: D
authors.initials: D
authors.lastname: Bénisti
authors.affiliation: CEA, DAM, DIF, F-91297 Arpajon, France.
authors.forename: L
authors.initials: L
authors.lastname: Gremillet