Secondary-ion mass spectrometry was used to study Ti-concentration profiles in the depth direction and at the surface of near-stoichiometric Ti:LiNbO3 strip wave-guides fabricated using phase transport equilibration and co-diffusion of Ti-metal strips. The results showed that the profile of the Ti concentration along the width direction on the wave guide surface could be fitted by a sum of 2 error functions. In the depth direction, the Ti concentration obeyed a complementary error function or a generalized Gaussian function. The surface Ti concentration, 1/e width and depth, and mean diffusivities in the width and depth directions of the guide were, 1.04 x 1021/cm3, 8.5µm, 6.3µm, 0.18 and 0.1µm2/h, respectively. The 2-dimensional refractive index profile in the near-stoichiometric wave-guides was constructed indirectly by assuming a linearity between the Ti-induced index change and the Ti concentration. The surface refractive index increments at 1545nm were evaluated to be 3.132 x 10-3 and 1.186 x 10-2.

Secondary-Ion Mass Spectrometry Study on Near-Stoichiometric LiNbO3 Strip Waveguide Fabricated by Vapour Transport Equilibration and Ti Co-Diffusion. D.L.Zhang, Z.Yang, W.H.Wong, E.Y.B.Pun: Philosophical Magazine, 2007, 87[1], 63-75