Modeling Pulse Shape Distortions in the OMEGA Laser

We present a study of two potential sources of pulse shape distortion: Stimulated Brillouin Scattering (SBS) in optical fibers and a gain grating in the active medium of the regenerative amplifier. SBS, the major contributor to nonlinearities in optical fibers, is shown to be insignificant in OMEGA. Scattering from the gain grating formed in the laser crystal was included into a model of regenerative amplification. The developed model demonstrates good agreement with experiment. The model is not yet complete, but may have the potential to identify and explain other pulse shape distortions in the OMEGA front end. The mission of the OMEGA Iaser is threefold: to conduct implosion experiments and basic physics experiments in support of the National Inertial Confinement Fusion (ICF) program, to develop new laser and materials technologies, and to conduct research and development in advanced technology related to high-energy-density phenomena. The Iaser begins with a monomode laser, which emits a 200-nanosecond Gaussian optical pulse. A 20 ns square pulse is cut from its peak and is focused into a fiber, where it reaches high intensities. The pulse enters a puke shaping system, which shapes the pulse according to its settings. The pulse is then sent t