Strip waveguides in LiNbO3fabricated by combined metal diffusion and ion implantation

Embedded strip waveguides in LiNbO3are fabricated by a titanium in-diffusion followed by a masked implantation of helium ions which reduces the refractive index in the unmasked regions and confines the optical wave. This technique yields waveguides with well-defined lateral dimensions and strong optical confinement. The index profiles of helium implanted LiNbO3are determined with an index reduction of more than 1 percent up to about 1 μm depth for 350 keV He+ ions at a dose cm^-2. Electrooptic devices with self-aligned electrodes are fabricated by using the implantation mask as a lift-off mask, and Mach-Zehndet type interferometers are investigated.