Laser plasma interaction (LPI) was always a key issue in inertial confinement fusion (ICF) and has received extensive attention. The LPI processes, such as stimulated Brillouin scattering (SBS), stimulated Raman scattering (SRS) , double plasma decay (TPD), and inter-beam energy transfer (CBET), can cause consequences such as energy dissipation, disturbance of the plasma state, and generation of super-heated electrons to preheat the target pellet, and so on, whether in direct or indirect drive. Thus, it is an urgent task to suppress or control the related LPI processes. To this end, researchers have conducted a large number of experimental and theoretical work over the years. The ignition success of the U.S. NIF shows that these are the work is fruitful, but for the inhibition of LPI still need further research.
In recent years, broadband laser has gradually become a possible technology to suppress LPI. Increasing the bandwidth of the laser not only reduces the coherence of the driving laser, but also reduces the effective electric field strength in the plasma, which is directly related to the LPI process. The Shanghai Institute of Laser Plasma (SILP) has established a high-power broadband two-frequency laser facility, Kunwu, which can provide broadband lasers with a center wavelength of about 530 nm, a bandwidth of about 3 nm, a temporal coherence of less than 300 fs, and an energy of several hundred J. Based on this facility, some experimental studies of broadband laser-driven LPI process have been carried out, and it has been initially verified that for the thick target case, the broadband laser can effectively suppress the backward SBS, and there is also a certain suppression effect for the backward SRS. However, the related research is still far from enough.
In this paper, we continue to aim the LPI problem of broadband laser-driven planar targets and carry out experimental measurements of backscattering under different thicknesses of planar targets. Preliminary experimental results show that the backscattering situations corresponding to targets of different thicknesses are quite different. These results are useful for a better understanding of the broadband laser itself, as well as the mechanism and law of LPI suppression by the broadband laser.

Laser plasma interaction,broadband laser,stimulated Brillouin scattering