Zirconium-diffusion-doped Ti:LiNbO₃ strip waveguide for integrated optics

We report Zr⁴⁺-doped Ti:LiNbO₃ strip waveguide fabricated by Zr⁴⁺-diffusion-doping followed by diffusion of 8 μm wide, 100 nm thick Tistrips on a Z-cut congruent substrate. Optical study shows that the waveguide well supports both TE and TM, is single-mode at the 1.5 μm wavelength, and has a loss ≤ 1.3/1.5 dB/cm for the TE/TM mode. Secondary ion mass spectrometry study shows that the Zr⁴⁺-profile part having a Zr⁴⁺-concentration above the threshold of photorefractive damage covers 60% (70%) ordinary (extraordinary) index profile in the waveguide. We conclude that the waveguide is optical-damage-resistant.