Self-focusing effects in large, high power laser amplifiers become manifest as small-scale beam instabilities and as large-scale phase aberrations. Spatial filtering has been shown to control instabilities; spatial filters constitute appropriate lens pair elements for image relaying as well. In this paper, image relaying is presented as a technique for preserving the transverse intensity profile of a high power beam as it propagates long distances through nonlinear elements. As a consequence, amplifier apertures can be filled more effectively, leading to a doubling of fixed-aperture system performance. A rationale for optimal selection of spatial filter bandpass is also presented. This selection, as might be expected, depends upon details of the beam's spatial structure as it enters any filter. A geometrical optics approach is used throughout; nevertheless, derived results remain valid when diffraction is included.

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Certain damage observed on the optics in NOVA is consistent with a phenomenon akin to holographic imaging. (NOVA is the Lawrence Livermore National Laboratory's 10-beam Nd:glass laser used for inertial confinement fusion research.) The minimization of similar damage in next-generation laser systems is sought by first identifying the sources for these holographic images, specifying glass parameters appropriately, and staging the amplifier chain to circumvent the problem. The insight gained has lead to an explanation for a 20-year-old puzzle.

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