Broadband lasers have recently attracted significant attention as novel driving light sources and promising tools for mitigating laser-plasma instabilities (LPI). Recent broadband laser experiments indicate that, at high intensities, the Stimulated Raman Scattering (SRS) reflectivity driven by broadband lasers exceeds that driven by monochromatic lasers, and that broadband laser drive produces a larger population of hot electrons. In this study, we account for the speckle structure of realistic laser fields. We find that SRS is first triggered in regions containing high-intensity speckles. The generated hot electrons then diffuse into surrounding regions, promoting the onset of SRS there. Due to the temporal fluctuations inherent to broadband lasers, the overlap of high-intensity temporal spikes with strong spatial speckles leads to more intense SRS bursts. During the arrival of these high-intensity pulses, SRS produces a larger number of hot electrons, whose subsequent diffusion further enhances SRS growth in neighboring regions. As a result, both the SRS reflectivity and the number of superthermal electrons are higher under broadband laser drive than under monochromatic laser drive.
 

broadband laser,Stimulated Raman Scattering,speckle,nonlinear evolution,hot electron