Syncnrotron X-ray Diffraction Imaging of Photorefractive Crystals

Signal processing in photorefractive crystals is complicated by photore­fractive amplified scattering (fanning). The scattering centers responsible for seeding the fanning noise may be presumed to be traceable to crystal lattice irregularities. These defects have not yet been examined in any great detail, and the relative importance of various specific imperfections and the role they play in the crystal optics are not known. An understanding of these defects should lead to improvement in signal processing through growth of more satisfactory photorefractive crystals. We have set out to address these problems through direct, in situ observation of photorefractive crystals and their gratings in barium titanate by high resolution monochromatic synchrotron x-ray diffraction imaging. The results that we report here indicate the nature of the principal limiting imperfections and demonstrate the feasability of direct observation of photorefractive gratings and scattering centers.