This project has the goals of fabricating waveguides in LiNbO3 and LiTaO3 with a controlled ferroelectric domain structure in two different ways, with the final objective of efficient Second Harmonic Generation (SHG). In the first part, the goal is to achieve periodic reversal of ferroelectric domains by using pulsed thermal excitation with laser pulses. With this novel laser technique it is expected to directly obtain the periodic pattern; this will be used for Quasi-Phase-Matching SHG. In the second part, by Laser Ablation Technique I will deposit and diffuse thin films that will create large and gradual changes in the Curie Temperature with the goal of obtaining, inside the waveguide, an alternative domain structure in the transverse direction to the surface (by alternative poling at the different temperatures). This will improve the overlap between either guided mode or to Cerenkov mode.