Precise determination of refractive-index changes in Ti-diffused LiNbO3 optical waveguides

Abstract

A new method for determining refractive-index changes in Ti-diffused LiNbO3 optical waveguides is reported. The measurement process was as follows: (1) Diffusion profiles and Ti concentrations in LiNbO3 optical waveguides were measured by an x-ray microanalyzer. (2) Ti concentrations in the samples were converted into refractive-index changes using calibration curves which gave the relation between Ti concentrations and refractive-index changes. The calibration curves were obtained from highly Ti-diffused LiNbO3 samples, as well as Ti-doped LiNbO3 single crystals. As an example, the maximum refractive-index changes of a Ti-diffused LiNbO3 optical waveguide made at 1000 °C for 10 h were determined to be Δne=1.05×10−2 and Δno=7.7×10−3.