Low-loss, damage-resistant optical waveguides in Zn-diffused LiNbO3 by a two-step procedure

In the present work the fabrication of high-quality LiNbO3 waveguides, based on Zn diffusion from vapor phase using a two-step diffusion process, has been demonstrated. The optical waveguides fabricated using this method have low propagation losses (less than 0.5 dB/cm measured at 633 nm), as a consequence of the high surface quality obtained. High photorefractive damage resistance is reported, and it has been related to the Zn incorporation into the LiNbO3 crystals. Additional advantages of this waveguide fabrication method due to the low temperature of the process (<900 °C) are to prevent Li out-diffusion and to preserve ferroelectric domain structures.