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.