Stress in LiNbO3 proton-exchanged waveguide layers

Penetration of hydrogen ions in the crystal lattice of LiNbO3 certainly causes stress in the proton-exchanged region, especially when the level of doping is high. In the present study, a correlation between stress and the level of doping (respectively, between stress and the phase composition of the measured layer) has been obtained. Proton-exchanged waveguide layers in X, Y and Z-cut LiNbO3 have been produced at different technological conditions. These layers have been studied by spectroscopic methods for analyzing their phase composition and by the optical integral method for stress measurements. The intrinsic stress which contributes to the better characterization of such optical waveguides was calculated. An attempt to indicate stress correlation to the relative quota of the different phases in the proton exchanged layer is made.