Wavelength dispersion of Ti induced refractive index change in LiNbO 3 as a function of diffusion parameters

Z -cut X -propagating, LiNbO 3 :Ti planar waveguides have been characterized over a wide range of diffusion conditions. Measurements of Ti concentration and refractive indexes have revealed Gaussian profiles. Their dependence with diffusion conditions have been studied. The relation, established at several wavelengths ( \lambda = 0.6328 \mu m, 1.1523 μm, 1.523 μm), between extraordinary and ordinary refractive index change \Deltan_{e,0}(z) and titanium concentration C(z) is found to be nonlinear and of the form: \Deltan_{e,0}(z) = A_{e,0}(C_{0},\lambda) (C(z))^{\alpha_{e,0}} While \alpha_{e,0} is a constant, the proportionality coefficient A_{e,0} depends not only on the wavelength λ, but also on the diffusion conditions, characterized by C 0 , the Ti surface concentration of the diffused guide. Such a nonlinearity of Ti diffusion in LiNbO 3 has been revealed thanks to a complete and wide range investigation on both indiffused Ti and index profiles.