Optical-Damage-Resistant Ti-Diffused LiNbO3 Strip Waveguide Doped With Scandium

We report Sc³⁺-doped Ti:LiNbO₃ (Ti:Sc:LN) strip waveguide fabricated by Ti-diffusion following homogeneous Sc³⁺-diffusion-doping in a Z-cut congruent substrate. We show that Sc³⁺-doping has little contribution to the substrate index and the Li₂O out-diffusion was effectively suppressed. The refractive index increases in the waveguide layer are mainly contributed from the Ti⁴⁺ dopants. The waveguide well supports both transverse electric (TE) and magnetic (TM) modes, is single-mode at 1.5- \(\mu \) m wavelength, and has a loss of 1.4 dB/cm for the TE mode and 1.8 dB/cm for the TM mode. A secondary ion mass spectrometry study shows that the Sc³⁺-profile covers 80% ordinary refractive index profile and almost 100% extraordinary refractive index profile, and the 1/e Sc³⁺ concentration is above the threshold of photorefractive effect. Further, two-beam hologram recording experimental results verify the optical-damage-resistant feature of the waveguide. Highlights are given for fabrication of an optical-damage-resistant Ti:Sc:LN waveguide.