Correcting inherent aberrations in the grating rhomb beam sampler

Abstract

The inherent aberrations are analyzed for the case of a two-grating rhomb laser beam sampler used in high energy laser systems. Although plane wave fronts are sampled without aberration, spherical or more complex wave fronts suffer 1-D phase and displacement deviations. An inverse filter description is developed that employs the angular spectrum concept for the incident and sampled beams. An inverse filter is easily synthesized and may be used to deconvolve the aberrations from a sampled data set. In addition, an optimization was performed in order to minimize phase errors in the sampled beam and to develop design criteria. Some practical examples are given which show that, in an optimized system, the aberrations are often negligible, and deconvolution is seldom necessary.