To achieve uniform irradiation, the focal spot from a high-power laser system must be homogeneous; thus, laser beam smoothing is required. In this study, we theoretically demonstrated a novel spatial smoothing method based on stimulated Brillouin scattering (SBS) in a plasma. As SBS is sensitive to pump intensity, the area of higher intensity in the laser beam has a higher reflectivity, leading to a more homogeneous passed beam. From the theoretical simulation, the laser beam modulation significantly decreased in SBS, while the fluence contrast decreased from 15.9% to 9.7%.

Pinpoint damage is the main type of bulk damage in potassium dihydrogen phosphate (KDP) crystals in high-power lasers. Using time-resolved microimaging, we observed the complete dynamic evolution of pinpoint damage in a KDP crystal. We analyzed changes in the patterns of dark zones formed by decreasing probe transmittance in transient images throughout the process. The mechanical properties of stress waves in KDP crystals were further studied by a depolarized shadowgraph experiment and theoretical simulation. The dynamic evolution of mechanical stress waves was observed, and the correlation between mechanical failure due to stress waves and the static characteristic damage morphology was established.