Wavelength dispersion of Ti induced refractive index change in LiNbO3as a function of diffusion parameters

Z-cutX-propagating, LiNbO3: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 (λ = 0.6328 , 1.1523 μm, 1.523 μm), between extraordinary and ordinary refractive index changee,0(z)and titanium concentrationC(z)is found to be nonlinear and of the form:e,0(z) = Ae,0(C₀,λ) (C(z))^{αe,0}Whileαe,0is a constant, the proportionality coefficientAe,0depends not only on the wavelength λ, but also on the diffusion conditions, characterized by C0, the Ti surface concentration of the diffused guide. Such a nonlinearity of Ti diffusion in LiNbO3has been revealed thanks to a complete and wide range investigation on both indiffused Ti and index profiles.