Growth and guided optical and surface acoustic wave properties of LiNbO3 thin films

Epitaxial LiNbO₃ films were successfully grown on α-Al₂O₃(001), (012) and (110) and LiTaO₃ (110 substrates) by RF magnetron sputtering. The optical guided wave propagation loss for those films was measured. The minimum optical propagation loss of the films was 6.47 dB/cm (TE₀ mode) for the LiNbO₃ film on LiTaO₃ The theoretical calculation of the surface wave coupling coefficient predicted that the most simple and realistic configuration with its interdigital transducer on top of the LiNbO₃ film and without the floating electrode gives the k² values as high as 20.9% for the first mode and 7.4% for the 0th mode for the surface acoustic waves propagating in the [110] direction of the (110) LiNbO₃ film on the (110) sapphire substrate, and values higher than 20% and 5.8% for those modes for the [12¯0] propagation on the (100) LiNbO ₃ film on the (012) sapphire substrate