Proton exchange of quasistoichiometric LiNbO3

Abstract

Quasistoichiometric LiNbO3 was used as substrate for proton exchanged waveguides prepared by immersion in hot benzoic acid for different times and melt compositions. Both α- and β-phase guides were investigated. Their basic properties were studied and compared with those of guides prepared under the same conditions on congruent substrates. For α-phase guides on quasistoichiometric substrates, the values of the index jump and the effective diffusion coefficient are, respectively, 0.53 and 0.54 times those obtained on congruent substrates under the same conditions. Also, their d33 coefficient for second harmonic generation is about 10% greater, while the optical damage resistance is a factor of 5 smaller. On the other hand, the properties exhibited by β-phase guides depend very little on the substrate stoichiometry. The results are discussed in terms of the lithium deficiency generated during the exchange in comparison to that previously existing in the substrate used.