Grating Evolution and Form in a Single-Crystal Self-Pumped Barium Titanate Phase Conjugator

We studied the evolution of patterns of scattered light in a barium titanate crystal, during the process of self-pumped phase conjugation in a system with no external beam-reflecting elements. We also studied the effect on the back-propagating phase-conjugate output of erasing small successive portions of the photorefractive volume grating. We interpret the results of these studies as indicating the formation of reflection gratings by feedback, from back-propagating beams produced by initial transmission gratings. The transmission gratings are initiated by power in reflective optical cavities between cube corners. The light in these cavities is the result of forward holographically amplified scattering (fanning). Transmission gratings, resulting from light back-scattered off the microrough edge of the cube, also contribute to the back-propagating beam.