Polarization switching of lithium niobate with giant internal field

We report a high-field analysis on the sidewise 180° domain motion in congruent-grown Z-cut lithium niobate (LiNbO3) crystals. Polarization switching in reverse poling is found to take place at a smaller field strength (E), exhibit a larger switching current (is), and substantiate a faster switching time (ts) compared with the forward poling case. Such an axial anisotropy is correlated to a defect-induced internal field Eint in the bulk and has a strength of 2.37 kV/mm and pointing along the crystal c axis. In the high-field regime ranging from 19 to 24 kV/mm, a linear dependence of is and 1/ts on E is resolved. These observations are ascribed to a fast nucleation process followed by a sidewise 180° domain expansion, whose velocity can be characterized according to νs=μs[E−(Ec±Eint)], where the threshold field Ec and mobility μs measure a strength of 18.74 kV/mm and 1.6±0.1 mm2/kV s, respectively.