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

Non-congruent LiNbO3 crystals has been used to determine the influence of the 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 defect density in the crystals. Moreover it is shown that it is possible to realign the ferroelectric domain structure of near-stoichiometric LiNbO3 crystals to prepare periodic poled structures which allows second harmonic generation at shorter wavelengths than with congruent crystals at a fixed wavelength.