Influence of the non-stoichiometry on the electro-optic properties in pure LiNbO3

We report, for the first time a complete set of electro-optic measurements of the r(c) and r(22) coefficients and of their corresponding dielectric permittivities in pure LN as function of the concentration of intrinsic defects related to the deviation from the stoichiometry. Non monotonous dependences of EO coefficient r(c) and r(22) are found to be closely linked to similar dependences of their corresponding dielectric permittivities. This behaviour can be attributed to the partial occupation by Nb ions of Li sites. The role of intrinsic defects are discussed to explain these behaviours. Particularly, the electromechanical contributions are considered.