Two-color-recorded photorefractive gratings in lithium niobate surface-doped with iron and copper

Permanent photorefractive gratings both in bulk and waveguide samples of some electrooptic crystals are promising elements for different applications in photonics. The most interesting dopants that significantly influence the photorefractive properties of LiNbO/sub 3/, are iron (Fe) and copper (Cu). In this paper, we investigate an influence of an incoherent green illumination to characteristics of photorefractive gratings which are recorded by the external coherent light beams in planar LiNbO/sub 3/ waveguides doped both with Fe and Cu.