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-mu m-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-stoichiometric environment. The waveguide well supports both the TE and TM modes, shows weak polarization dependence, is in single mode at the 1.5 mu m 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. (C) 2015 Optical Society of America