A numerical investigation of stimulated Brillouin scattering driven by broadband lasers in high-Z plasmas

The evolution of stimulated Brillouin scattering (SBS) driven by broadband lasers in high-Z plasmas is investigated using one-dimensional collisional particle-in-cell simulations. The temporal incoherence of broadband lasers modulates the pump intensity, generating stochastic intensity pulses that intermittently drive SBS. The shortened coherence time weakens the three-wave coupling and continuously reduces the temporal growth rate, while the saturated reflectivity remains nearly unchanged until the bandwidth exceeds a critical threshold. Simulations with varying laser intensities and bandwidths reveal a consistent empirical scaling behavior, indicating that effective SBS suppression occurs only when the laser bandwidth exceeds the SBS growth rate of the corresponding monochromatic case by approximately two orders of magnitude under the present simulation conditions. Comparative simulations in Au and AuB plasmas exhibit similar suppression trends, with AuB showing reduced SBS growth rate and reflectivity, and the onset of suppression occurring at a lower bandwidth. These findings elucidate the coupled dependence of SBS mitigation on laser bandwidth and intensity in high-Z plasmas, and may serve as a useful reference for evaluating broadband mitigation strategies in inertial confinement fusion.