Hydroxyl ions in stoichiometric LiNbO3 crystals doped with optical damage resistant ions

Abstract

The infrared spectra of stoichiometric LiNbO3 crystals containing photorefractive damage resistant ions (e.g. M=Mg, Zn, Sc, In, Hf, Zr or Sn) above their threshold concentration reveal OH− absorption bands absent in undoped crystals. The bands are attributed to stretching vibrations of hydroxyl ions in MNbn+–OH- (n=2, 3 or 4) type defect complexes. The higher the valency of the dopant ion the lower the observed frequency of the hydroxyl vibration in the complex, and the closer the O–H bond direction to the oxygen plane perpendicular to the crystallographic c axis of the crystal.