Combined phase, near field, and far field diagnostic for large-aperture laser systems

A method is described for extracting near field, far field and phase information from an interferogram of a laser system output generated by a self referencing, radial shear interferometer. The interferogram may be used as an amplitude mask of a coherent beam. This beam is numerically propagated to the far field where the laser output and its complex conjugate can be separated. The near field and optical phase difference map may then be extracted from the complex representation of the laser output obtained by propagating back to the near field. The practical application of this method and its limitations are discussed and compared with images from equivalent plane far field and near field cameras on the HELEN 2TW Nd:glass laser system.