PROTON-EXCHANGE OF QUASISTOICHIOMETRIC LINBO3

Quasistoichiometric LiNbO3 was used as substrate for proton exchanged waveguides prepared by immersion in hot benzoic acid for different tim es and melt compositions. Both alpha- and beta-phase guides were inves tigated. Their basic properties were studied and compared with those o f guides prepared under the same conditions on congruent substrates. F or alpha-phase guides on quasistoichiometric substrates, the values of the index jump and the effective diffusion coefficient are, respectiv ely, 0.53 and 0.54 times those obtained on congruent substrates under the same conditions. Also, their d(33) 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 beta-phase guides depend very little on the substrate stoichiometry . The results are discussed in terms of the lithium deficiency generat ed during the exchange in comparison to that previously existing in th e substrate used. (C) 1997 American institute of Physics.