A study of silver-film ion-exchanged glass waveguides in phosphate glass

In this work, properties of Ag thin-film ion exchange in Schott IOG-1 phosphate glass has been studied. Emphasis has been put on finding the proper diffusion parameters (self-diffusion coefficient for Ag + ions and the mobility ratio between the participating ions) at process temperatures of 90°C and 230°C. In order to extract the diffusion parameters a following procedure was utilized: An ion-exchanged slab waveguide was fabricated using the same process conditions as in the case of a two-dimensional waveguide fabrication. After slab waveguide fabrication, the effective refractive indices of the propagating modes were measured by prism coupling. Thereafter, a smooth refractive index profile was constructed by improved inverse Wentzel-Kramers-Brillouin method. This refractive index profile was compared with the Ag + ion concentration profile calculated from the diffusion equation by Crank-Nicolson method. The self-diffusion coefficient for Ag + ions and the ratio of the self-diffusion coefficients of Ag + and Na + ions were varied until convergence between the refractive index profile and the concentration profile was found. Using the diffusion parameters obtained from these experiments, two-dimensional waveguide mode profiles were calculated by finite difference method. These theoretically obtained mode profiles were compared with the measured mode profiles with different mask opening widths.