Ion exchange model for α phase proton exchange waveguides in LiNbO3

An H⁺/Li⁺ exchange model is found to be applicable to describe the diffusion of protons when optical waveguides are formed in LiNbO₃ by proton exchange methods where the proton doped crystal structure stays in the pure α phase. The H ⁺ and Li⁺ self-diffusion coefficients in the ion exchange model are determined as a function of the proton exchange temperature both for x-cut and z-cut LiNbO₃. In this way a very useful tool for predicting the proton concentration profiles and hence the refractive index profiles of α phase proton exchange LiNbO₃ waveguides is achieved