LARGE DIFFERENCES IN TI THERMAL-DIFFUSION CAUSED DOMAIN INVERSION BETWEEN UNDOPED AND MGO-DOPED LINBO3

The periodic modulation of domain polarizations by Ti thermal diffusio n on the + c face of LiNbO3 with and without MgO doping was studied sy stematically. It was shown that the depth of the inverted domain is qu ite different for these two substrates. Under the same fabrication con ditions, the depth of domain inversion in the MgO-doped substrate is l ess than one-tenth that of the undoped substrate. This large differenc e can be explained by the presence of MgO in LiNbO3, which decreases t he Ti diffusion constant and increases the minimum Ti concentration re quired for domain inversion.