Investigation of Stimulated Brillouin Scattering Driven by Broadband Lasers in High-Z Plasmas

TL;DR

This study uses simulations to analyze how broadband lasers influence stimulated Brillouin scattering in high-Z plasmas, revealing that increasing laser bandwidth can effectively suppress SBS growth, which is crucial for inertial confinement fusion.

Contribution

It provides a detailed analysis of SBS suppression mechanisms driven by broadband lasers in high-Z plasmas through particle-in-cell simulations, highlighting the critical bandwidth thresholds for effective mitigation.

Findings

Broadband laser incoherence reduces SBS growth rate.

Suppression occurs when bandwidth exceeds SBS growth rate by tens of times.

Similar suppression trends observed in Au and AuB plasmas.

Abstract

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 scaling behavior, indicating that effective suppression occurs only when the laser bandwidth exceeds the temporal growth rate of SBS by several tens of times. 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 bandwidth and laser intensity in high-Z plasmas, offering useful guidance for optimizing broadband laser designs in inertial confinement fusion.