The combination of X-ray absorption spectroscopy (XAS), suitable for determining the short range order around a chosen absorbing atom, with other techniques able to investigate the long range order (structure of the matrix), like Transmission electron microscopy (TEM) or wide angle X-ray scattering (WAXS), have enabled us to obtain some useful information about the way a rare earth is incorporated in oxide materials potentially interesting as optical devices, like TiO2, ZrO2 or LiNbO3. The concerned samples were elaborated, on the one hand by the ion-implantation technique, for the Er-implanted LiNbO3 single crystals, and on the other hand by sol-gel processing, for the Er-doped TiO2, or ZrO2 layers, respectively. Annealings were then performed at various times and temperatures after the dip-coating treatment and the ion-implantation respectively, leading to an erbium distribution profile that spreads up till 100 nm under the surface. The use of X-ray absorption spectroscopy (XAS) with the total electron yield detection mode (TEY), allows to probe a depth (under the surface) of about the same magnitude range, and reveals that the environment of the erbium ion, strongly depends on both its. concentration, the nature of the cation matrix, and the annealing conditions performed. This study put into evidence the need to built some phase diagram, and revealed the possibility to start them by means of XAS and TEM or WAXS, between the crystallized and amorphous states originated from the (Er, 0, matrix cation(s)) elements depending on the annealing temperature, before using these materials as optical devices. (C) 2003 Elsevier B.V. All rights reserved.