Role of stoichiometric point defect in electric-field-poling lithium niobate

Non-congruent LiNbO3 crystals has been used to determine the influence of t he intrinsic defect density in the ferroelectric domain inversion mechanism . The poling processes have been carried out either at high temperature or at RT throughout the electric-field-poling technique. It is shown that the coercive field of LiNbO3 crystals is strongly influenced by the intrinsic d efect density in the crystals. Moreover it is shown that it is possible to realign the ferroelectric domain structure of near-stoichiometric LiNbO3 cr ystals to prepare periodic poled structures which allows second harmonic ge neration at shorter wavelengths than with congruent crystals at a fixed wav elength.