Abstract
We report newly developed stoichiometric LiNbO_3 and LiTaO_3 crystals as promising materials for bulk quasi-phasematching using periodical poling because of its low coercive field for ferroelectric domain switching and reduced photorefraction as compared to congruent crystals. In this paper, we describe some differences in ferrelectirc domeain morphology between sloichiometric and congruent materials. Especially, in LiTaO_3, domain size was very large in stoichiometirc one that in congruent one. Lt turned out that the morphology is closely related with the contrability of periodical poling.
