Investigations on the UV photorefractivity of LiNbO(3):Hf.

The UV photorefractivity of LiNbO(3):Hf was investigated by beam distortion and two-wave coupling experiments. A sharp decrease of beam distortion was found between Hf concentrations of 2 and 2.5 mol.%, indicating a significant increase of photoconductivity there. The energy-transfer direction of the two-wave coupling and the effect of chemical reduction on the UV photorefractivity reveal that electrons are the carriers responsible for the UV photorefraction. Moreover, dissimilar with LiNbO(3) highly doped with Mg, Zn, and In, the grating recorded in LiNbO(3):Hf was found to be nearly stable in the dark but sensitive to red light, which can be attributed to the special location of Fe ions in the crystal lattice.