Self-enhanced diffraction properties of a nominally undoped barium titanate crystal with a thermally fixed grating

We describe recent studies on diffraction properties of a photorefractive barium titanate crystal having a thermally fixed grating. Buildup dynamics of diffracted signals are measured to analyze the contributions of ionic and re-created photocarrier (hole) gratings to the temperature-dependent diffraction efficiency in self-enhanced readout. An activation energy of mobile ions as nonphotoactive secondary carriers for fixing volume holograms is determined holographically. This value is compared with that of hydrogen ions estimated from polarization-dependent infrared absorption spectra in order to indentify the fixing species.