Comparison of crystal lattice changes caused by APE treatment of Er:LiNbO3 and by localised Er doping into LiNbO3 obtained by RBS-channeling and XRD analysis

Lithium niobate containing erbium (Er:LiNbO3), which is often used as non-linear optical material, was studied by Rutherford backscattering spectroscopy (RBS)-channeling analysis and X-ray diffraction (XRD). The Er3+ doping was done by both bulk doping and by localised doping. The studied samples were virgin Er:LiNbO3 wafers, and annealed proton exchange (APE) treated wafers in order to increase the refractive index in the surface layer and to create the planar optical waveguides. Moreover, erbium ions were introduced into the surface of pure LiNbO3 wafers by Er-moderate temperature localised doping. The APE:Er:LiNbO3 samples showed modifications of the crystal lattice compared to the virgin Er:LiNbO3; the Er localised doping samples even exhibited the tendency to form an amorphous surface layer in which the Er ions were incorporated.