Experimental investigation of short light pulse amplification using stimulated Brillouin backscattering

Efficient light amplification using stimulated Brillouin backscattering (SBS) in the strongly coupled regime has been predicted by numerical simulations. We experimentally investigated this regime by coupling two counter-propagating short pulses (a pump beam [0.4-30 ps, $\sim$10$^{16}$ W.cm$^{-2}$] and a seed beam, [400 fs, $\sim $10$^{15}$ W.cm$^{-2}$]), both at a wavelength 1.057 $\mu$m, in a preformed plasma. Diagnostics included energy and spectra of the transmitted pump and seed, and of the backscattered pump, as well as the duration of the transmitted seed. The spatio-temporal coherence of the transmitted pump (without seed) has been detected in order to gain insight in the SBS mechanism in this regime. Detailed results will be presented as a function of the plasma density, the ion species composing the plasma, and the polarisations of the pump and seed.