Enhancement of the amplitude and lifetime of photoinduced space-charge fields in multidomain ferroelectric crystals

We demonstrate that the amplitude and lifetime of optically induced space-charge gratings can be dramatically increased in ferroelectric barium titanate by partially depoling the crystal prior to grating recording. By repoling the crystal this space-charge grating produces a refractive index grating capable of diffracting light much more than a grating created in a well-poled, single-domain crystal. This effect is explained in terms of an electric compensation of free charge by the bound charge of the ferroelectric domain walls.