Picosecond blue-light-induced infrared absorption in single-domain and periodically poled ferroelectrics

Picosecond blue-light-induced infrared absorption is investigated in bulk and periodically poled ferroelectrics known to have high photorefractive resistance (KTiOPO4, MgO-doped congruent LiNbO3, MgO-doped stoichiometric LiNbO3, MgO-doped stoichiometric LiTaO3, and KNbO3). KNbO3 and MgO-doped congruent and stoichiometric LiNbO3 show the lowest susceptibility to induced absorption. Periodic poling slightly increases the susceptibility to the induced absorption in all materials but most noticeably in KTiOPO4, MgO-doped stoichiometric LiTaO3, and KNbO3. Different dynamics of induced absorption are investigated. Relatively high thresholds for induced absorption were observed in MgO-doped stoichiometric LiTaO3 and KNbO3. By increasing the peak power intensity of blue light, the induced absorption for LiNbO3, KTiOPO4, and KNbO3 are saturated, while in MgO-doped stoichiometric LiTaO3, the induced absorption increases almost linearly with the blue peak intensity. The low susceptibility to induced absorption observed in KNbO3 corroborates well with the earlier proposed existence of very shallow traps close to the valence band.