Influence of Hf ions in the formation of periodically poled lithium niobate structures

Periodically poled lithium niobate bulk crystals doped with hafnium have been grown by the off-centred Czochralski technique. The role of I-If ions in the formation of periodic poled structures has been characterized by structural and compositional techniques. A periodical modulation in Nb and in Hf concentration, as a function of the initial Hf concentration in the melt, has been observed. The periodic modulation observed in Hf and/or Nb concentration along the periodic structure has been attributed to the special feature in the incorporation of Hf ions into the LiNbO3 lattice. The shape of the solid-liquid interface influences the formation of the periodical structure and the character of the compositional modulation.