Push-pull integrate-optics Mach-Zehnder interferometer with domain inversion in one branch.

We report on a push-pull integrated-optics Mach-Zehnder interferometer having one domain-inverted branch and one noninverted branch. It is fabricated in the c(+) side of a LiNbO(3) substrate. We achieve ferroelectric domain inversion in one branch of the waveguide by doping it more heavily with Ti than the other branch and by using a high-temperature treatment that raises the temperature above the doped Curie temperature of the one branch but not of the other. The cumulative electro-optic effect of the inverted branch is found to be opposite that in the noninverted branch when both are subjected to the same electric field.