  The strong-coupling mode, called quasimode, will be excited by stimulated
Brillouin scattering (SBS) in high-intensity laser-plasma interaction. And SBS
of quasimode will compete with SBS of fast mode (or slow mode) in multi-ion
species plasmas, thus leading to a low-frequency burst behavior of SBS
reflectivity. The competition of quasimode and ion-acoustic wave (IAW) is an
important saturation mechanism of SBS in high-intensity laser-plasma
interaction. These results give a clear explanation to the low-frequency
periodic burst behavior of SBS and should be considered as a saturation
mechanism of SBS in high-intensity laser-plasma interaction.
