Precise determination of refractive index and thickness in the Ti-diffused LiNbO_3 waveguide

Diffusion depth and maximum refractive index change in the Ti-diffused LiNbO3 waveguide have been determined using a prism coupling method that takes into account the measuring accuracy. Calculation has been carried out by putting only the mode synchronous angles, measured with a GaP prism, into the computer program based on Marcuse’s WKB approximation. Results on LiNbO3 waveguide parameters are Δne = 0.007, d = 4.1 μm, and Δn0n0.005, d = 6.6 μm, respectively, under the Ti metal (500 Å) diffusion at 1100°C for 10 h in air.