A comparative study of silver diffusion in a glass substrate for optical waveguide applications

Multimode optical waveguides are fabricated in two steps by electrodiffusion of silver ions in a soda-lime glass from a metallic coating and are characterized by the methods of integrated optics. In the first step, the electromigration process and the fabrication parameters are controlled through electrical measurements, and an effective diffusion coefficient is calculated at 230 degrees C from the Nernst-Einstein relation as well. In the second step, a new experimental method, allowing the calculation of silver and sodium self-diffusion coefficients, is presented. It is based on the diffusion equation from which it is shown that, for two given values of ion concentrations, the two diffusion coefficients are deduced. Both diffusion coefficients and optical properties of the waveguides are discussed and compared to the results of other works with which we find good agreement.