In this work the Formation of optical waveguides in periodically poled Lith
ium niobate (PPLN) substrates by Zn-diffusion from vapour phase is studied.
It has been found that the diffusion of the Zn ions is homogeneous in the
PPLN substrates and the optical waveguides can be fabricated with the same
parameters used in single-domain lithium niobate. The periodic ferroelectri
c domain pattern initially present in the substrate is preserved in the wav
eguides.