Production of petawatt laser pulses of picosecond duration via Brillouin amplification of nanosecond laser beams*

The demonstration of fast-ignition (FI) inertial confinement fusion (ICF) requires the delivery of 40 kJ - 100 kJ of laser energy to the hot spot within 16 ps, preferrably at near-infrared wave lengths (351 nm). However, high-energy picosecond petawatt beams at 351 nm are extremely difficult to generate using conventional solid-state laser systems. Previous studies have shown that Raman amplification in plasma is a potential route for the production of petawatt pulses of picosecond duration at 351 nm [Trines et al., PRL, 2011]. In this paper we show, through analytic theory and particle-in-cell simulations, that similar results can also be obtained through Brillouin amplification of a short seed laser beam off a long pump beam at moderate intensity. Scaling laws governing the optimal parameter space for pump beam, seed beam and plasma will be derived using a self-similar model for Brillouin scattering, and verified via simulations. A comparison with Raman scattering will be made, to determine which scheme is most suitable for a range of laser-plasma configurations.