Gallium-diffused waveguides in sapphire

The fabrication and characterization of gallium-diffused planar waveguides in sapphire are reported. Waveguides were fabricated by diffusion of 60–200-nm-thick films of gallium oxide into $c$-cut sapphire at 1600 °C for times ranging from 6 to 16 h. Near-field intensity profiles of the guided modes were measured at wavelengths from 488 to 850 nm, and the surface-index elevation was estimated to be up to $\left(0.6\pm 0.02\right)\times {10}^{-2}$. Potential applications for low-threshold Ti:sapphire waveguide lasers and for optical integrated circuits with passive and active elements in sapphire are discussed.