Contribution of diffused Er3+ ions to refractive index of LiNbO3 crystal and relation of Li out-diffusion to Er3+-diffusion condition were studied. Three X-cut and three Z-cut congruent LiNbO3 plates locally coated with 10, 15, or 20 nm thick Er metal films were annealed at 1100 or 1130C for 60 or 100h under different atmospheres of surrounding air, wet O2 or wet Ar. After the anneal, the ordinary and extraordinary refractive indices at Er3+-doped and Er-free parts of crystal surface were characterized at the 633, 1311 and 1553nm wavelengths by measurement of critical angle. The difference of surface index values at the Er3+-doped and Er-free parts enables to identify the Er3+-doping effect on substrate index. From the known birefringence, the surface Li2O contents at the Er3+-doped and Er-free parts were evaluated. A comparison with the Li2O content data before the anneal treatment allows to obtain the anneal-induced Li2O loss and hence identify the anneal condition effect on the Li out-diffusion. The results show that the contribution of Er3+-doping to the ordinary index was within the measurement error of 10-3 and that to the extraordinary index was within ±1.7 x 10-3, which was just slightly out of the measurement error. The diffusion temperature was while the diffusion environment was not the key factor responsible for the Li2O out-diffusion

Contribution of Diffused Er3+ Ions to Refractive Index of LiNbO3 Crystal and Relation of Li Out-Diffusion to Er3+-Diffusion Condition. Z.Wang, P.R.Hua, F.Han, D.Y.Yu, E.Y.B.Pun, D.L.Zhang: Journal of the American Ceramic Society, 2012, 95[6], 1993-7