Optical losses in metal/SiO ₂ -clad Ti:LiNbO ₃ waveguides

We present measured excess loss resulting from electrode overlays for both TE and TM polarisations as a function of SiO2 buffer layer thickness for Ti:LiNbO3 strip waveguides at λ = 1.32 μm. We find there is negligible excess loss to the TE mode with no buffer layer and that the excess loss to the TM mode can be essentially eliminated with a SiO2 layer only 700 Å thick. A passive polariser with ̃ 1.5 dB fibre-waveguide-fibre insertion loss and > 13 dB extinction ratio is also demonstrated.