SIMS analysis and optical study of annealed iron-doped LiNbO3 crystal

The distribution of iron content along the depth of annealed LiNbO3 substrates has been measured by the secondary ion mass spectrometry (SIMS). It is found that Fe out-diffuses to the surface of annealed LiNbO3 crystals, causing a high content of Fe in a thin surface layer. Planar waveguides have been fabricated from both unannealed and annealed crystals by the proton exchanged method, and two-wave mixing experiments have revealed an enhanced photorefractive effect in the waveguide of the annealed LiNbO3 crystal.