Since 1987, an intensive Portuguese-Spanish collaboration program has been developed on microstructural characterization of LiNbO3 by nuclear (ion-beam and hyperfine interaction) techniques. The collaboration involves the Department of Applied Physics of the Universidad Autónoma de Madrid, on the Spanish side, and the Center of Nuclear Physics and the Department of Physics of LNETI, on the Portuguese side. The combined effort of the two latter institutions is now channeled through the recently created Center for Materials Characterization and Processing.
LiNbO3 is an important material for optoelectronic applications, including light modulation, microwave filters, frequency doublers, and those applications based on the photorefractive effect. Photorefractive applications, still at the laboratory level, include holographic information storage, coherent beam amplification, beam deflectors, and applications relying on the production of phase-conjugated beams by four-wave mixing. LiNb03 is particularly useful for optical information processing, optical interconnects, associative memories, and neural net implementations. These applications involve bulk LiNbO3, but mostly waveguide structures fabricated in LiNbO3 substrates. Recently the development of efficient waveguide lasers on ion-implanted and proton-exchanged waveguides has opened a new field whose final objective is the fabrication of integrated laser modulators and frequency doublers on the same “chip.” The mastering and optimization of all these applications rely on an adequate microstructural characterization of the material with particular reference to both intrinsic and extrinsic point defects. The knowledge and control of this microstructure should permit the fabrication of well-characterized and reproducible devices.