Optical damage in x-cut proton exchanged LiNbO3 planar waveguides

The optical damage of different proton exchanged LiNbO3 planar waveguides has been experimentally studied by measuring the intensity output of a single beam as a function of the intensity input. Parallel measurements of photovoltaic currents (sometimes referred to as photocurrents) have been carried out with the same setup as a function of the input intensity and they have been correlated to the optical damage data. The following proton exchanged phases have been studied and compared with the substrate: alpha, beta(1), beta(2), and reverse proton exchanged (RPE). The greatest intensity thresholds for optical damage, about 2x10(3) times greater than that of the substrate, have been obtained in RPE guides supporting ordinary polarization and in beta(1,2) guides which support extraordinary polarization. On the other hand, the lowest photovoltaic currents have been measured in beta(1,2) phases. As a function of the light intensity, the strong superlinear behavior exhibited by the photovoltaic current in the alpha phase is almost absent in the others. In addition, it has been experimentally ascertained that a scattering increase produces a decrease of the threshold intensity for optical damage. The role of those different effects is discussed extensively together with the electro-optic properties of the different guides. (c) 2006 American Institute of Physics.