Correlation between structural and optical properties in proton-exchanged LiNbO₃

We present a correlation of the structural characterization of proton-exchanged LiNbO₃ provided by ion beam and x-ray analysis with the optical characterization provided by refractive index and second-harmonic generation measurements. The process of proton exchange induces disorder in the crystal lattice of LiNbO₃. Subsequent thermal annealing removes only partially the lattice disorder and, in particular, the near surface region of the samples generally remains highly distorted. Results of x-rays studies indicate that the proton exchange induces a strain in the lattice and thermal annealing partially recovers it.