Optical waveguides in LiTaO_3: silver lithium ion exchange

Abstract

Silver lithium ion exchange has been found to produce optical waveguides in x-cut LiTaO₃ at temperatures well below the Curie temperature, producing waveguides that require no repoling. This process is attractive for integrated optics because LiTaO₃ is less susceptible to optical damage and has much lower birefringence than the more commonly used LiNbO₃ substrate. The exchange process has been studied as a function of temperature. Diffusion coefficients, activation energy, losses, and temperature dependence of the extraordinary index change are given. Index increases of Δn_e ∼ 0.03–0.05 at λ = 632.8 nm and losses of 0.8–1.3 dB/cm for the TE₀ mode are comparable with values for Ti-diffused guides in LiNbO₃, making this technique potentially useful for integrated optics applications.