Titanium diffusion is a wavehuide process that consists of diffusing titanium atoms in the crystalline lattice in order to locally increase the refractive index. The fabrication begins with the titanium deposit to be diffused by photolithography and lift-off. Once the titanium layer has been placed on the surface of the wafer, we move on to high temperature diffusion of the titanium in the crystal. The profile of the index obtained depends on the thickness of the titanium layer, the temperature and the length of diffusion. At this time there is a local increase of the refractive index according to the extraordinary axis and also according to the ordinary axes. Contrary to the proton exchange technique, the two light polarizations are guided.