Non-stoichiometric control of LiNbO_3 and LiTaO_3 in ferroelectric domain engineering for optical devices

摘要

Photorefractive damage, photoconductivity, and photogalvanic currents of stoichiometry controlled LiNbO_3 and LiTaO_3 have been investigated. A nearly stoichiometric LiNbO_3 single crystal shows a lower photorefractive damage resistance than congruent LiNbO_3, however, crystals doped with a small amount of MgO (>0.78 mol. percent) exhibit no measurable photorefractive damage at 532 nm up to intensities of 2 MW/cm~2. In the case of LiTbO_3, it turned out that nearly stoichiometric crystals exhibit considerably high damage resistivity even without MgO doping. Green-induced infrared absorption (GRIIRA) in the crystals was also investigated by a photothermal technique. The GRIIRA in nearly stoichiometric LiNbO_3 is found to be remarkably decreased by a small amount of MgO. GRIIRA in nearly stoichiometric LiTaO_3 was strongly suppressed even without MgO doping.