Proton-Exchanged LiNbO₃Optical Waveguides Using Stearic Acid

Proton-exchanged optical planar waveguides have been fabricated in z-cut LiNbO3 using a new proton source: stearic acid. These waveguides were characterized optically and were found to exhibit a step index profile with Δ n = 0.118 measured at 0.633μm. The propagation losses were typically around 1.5 dB/cm, and the diffusion constant Do and the activation energy Q for the proton-exchange process were measured to be 5 × 10⁶ μm ²/h and 69 kJ/mol, respectively. The diffusion rate using stearic acid is the slowest reported for proton-exchange process using acidic media.