Near-stoichiometric Ti-diffused LiNbO₃ strip waveguide doped with Zr⁴⁺

We report a near-stoichiometric Ti:Zr:LiNbO₃ strip waveguide fabricated from a congruent substrate with a technological process in the following sequence: Zr⁴⁺-diffusion-doping, diffusion of 8-μm-wide, 100-nm-thick Ti strips, and post-Li-rich vapor transport equilibration. We show that Zr⁴⁺-doping has little effect on the LiNbO₃-refractive index, and the waveguide is in a near-stoichiomet ric environment. The waveguide well supports both the TE and TM modes, shows weak polarization dependence, is in single mode at the 1.5 μm wavelength, and has a loss of ≤0.6/0.8 dB/cm for the TE/TM modes. A secondary ion mass spectrometry analysis shows that the Zr⁴⁺-profile part with a concentration above the threshold of photorefractive damage entirely covers the waveguide, implying that the waveguide would be optical-damage resistant.