Fabrication of magnesium-oxide-induced lithium outdiffusion waveguides

A short-time high-temperature diffusion process for the fabrication of the lithium niobate (LiNbO/sub 3/) optical waveguide with a magnesium-oxide (MgO) strip-loaded structure is presented. The deposited MgO layer causes the lithium to diffuse out of the LiNbO/sub 3/ substrate. The secondary ion mass spectroscopy (SIMS) data of the fabricated waveguide show that the lithium diffuses out of the substrate and gets into the MgO cover layer, which results in an increase in the extraordinary refractive index of the substrate. In particular, it is found that the diffused atoms are piled up near the LiNbO/sub 3/ and MgO interface. Also, the electrooptic effect of the fabricated waveguide is better than that of the conventional titanium-indiffused waveguide. Moreover, single-mode and single-polarization waveguides can be easily obtained without any significant surface guiding or surface damage on the crystalline substrate.<>