Smoothing, caused by the small-spatial-scale B integral, was measured on the OMEGA laser (a high-power, solid-state laser used for inertial confinement fusion research) without applied bandwidth. The intrinsic nonuniformity of laser irradiation [i.e., irradiation without smoothing by spectral dispersion] was determined from fluence distributions in equivalent-target-plane images of beams with phase plates. These data are compared with simulations that include both small-spatial-scale and whole-beam B integrals. The nonuniformity decreases with increasing average intensity. High-intensity beams can acquire bandwidth as a result of the intensity-dependent phase accumulated in the laser chain. The far-field speckle pattern produced by a phase plate can shift as the near-field phase front changes, which decreases the nonuniformity. The far-field power spectrum is affected mainly in the high spatial frequencies, where it is not expected to mitigate hydrodynamic instabilities.
© 2002 Optical Society of America
(030.0030) Coherence and statistical optics : Coherence and statistical optics
(030.6140) Coherence and statistical optics : Speckle
(190.5940) Nonlinear optics : Self-action effects
(350.2660) Other areas of optics : Fusion
(350.5500) Other areas of optics : Propagation
J. A. Marozas, S. P. Regan, J. H. Kelly, D. D. Meyerhofer, W. Seka, and S. Skupsky, "Laser beam smoothing caused by the small-spatial-scale B integral," J. Opt. Soc. Am. B 19, 7-17 (2002)