Investigation of Optical Smoothing Techniques on Multiple Beams *

Intense laser hotspots/speckles are a concern on high power laser facilities due to their role in seeding unwanted instabilities such as SBS (Stimulated Brillouin Scattering). Optical smoothing techniques such as SSD^1,2 (Smoothing by Spectral Dispersion) are used to better homogenize the laser focal spot intensity pattern on the time scale of the instabilities. Here we report on a project that examines the combined laser electric fields of overlapping NIF beams including the effects of SSD, polarization rotation, and beat waves³. An overview of the simulation technique will be presented with updates on characterizing various optical smoothing techniques.

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2)J. Garnier and L. Videau, "Statistical analysis of the sizes and velocities of laser hot spots of smoothed beams", Physics of Plasmas 8, 4914-4924 (2001) https://doi.org/10.1063/1.1405127

3)P. Michel, W. Rozmus, E. A. Williams, L. Divol, R. L. Berger, S. H. Glenzer, and D. A. Callahan , "Saturation of multi-laser beams laser-plasma instabilities from stochastic ion heating", Physics of Plasmas 20, 056308 (2013) https://doi.org/10.1063/1.4802828