Large differences in Ti thermal diffusion caused domain inversion between undoped and MgO-doped LiNbO3

The periodic modulation of domain polarizations by Ti thermal diffusion on the +c face of LiNbO3 with and without MgO doping was studied systematically. It was shown that the depth of the inverted domain is quite different for these two substrates. Under the same fabrication conditions, the depth of domain inversion in the MgO-doped substrate is less than one-tenth that of the undoped substrate. This large difference can be explained by the presence of MgO in LiNbO3, which decreases the Ti diffusion constant and increases the minimum Ti concentration required for domain inversion.