OPTICAL AMPLIFICATION SYSTEM WITH NON-ORTHOGONAL SIGNAL AND DISTRIBUTED MULTI-PUMP BEAMS AND PHOTOREFRACTIVE CLEANUP

An optical amplification system directs a diffraction-limited signal beam through a series of crossings, at substantially less than 90.degree. crossing angles, with a number of non-diffraction-limited pump beams in a photorefractive medium. The pump beams are e-polarized while the signal beam travels down the crystal medium's c-axis and is polarized in the same plane as the pump beam polarization, resulting in an energy transfer from the pumps to the signal beam while leaving the signal beam diffraction-limited. The photorefractive medium is preferably a series of BaTiO.sub.3 :Rh crystals that are aligned parallel to the angled edge of a wedged-shape prism through which the pump beams are transmitted, with the crystals cut so that their C-axes are parallel to the signal beam.