Abstract

Proton exchanged LiNbO₃ optical waveguide fabrication [1] has attracted considerable attention because of the ease of fabrication, relatively low temperatures at which it can be carried out, large index difference (Δn ~ 0.12) it produces and the high optical damage threshold of the resulting guides. Several authors [2-3] have reported the diffusion analysis of such proton exchanged guides by measuring the depth of the waveguide d, as a function of exchange time t and then assuming the linear relationship d = [4D(T)t]^1/2 to deduce the effective diffusion coefficient D(T). Such a linear diffusion relationship, which takes into account the constancy of proton concentration in the melt as the diffusion proceeds, predicts that the amount of protons in the crystal should increase linearly as a function of square root of exchange time. This would be the case if the melt is of 'infinite' volume.

© 1988 Optical Society of America