  A standardized phase retrieval algorithm is presented and applied to an
industry-grade high-energy ultrashort pulsed laser to uncover its spatial phase
distribution. We describe in detail how to modify the well-known algorithm in
order to characterize particularly strong light sources from intensity
measurements only. With complete information about the optical field of the
unknown light source at hand, virtual back propagation can reveal weak points
in the light path such as apertures or damaged components.
