Silver film-diffused glass waveguides: Diffusion process and optical properties

Diffusion of a silver film into a glass substrate in the presence of an electric field is used to fabricate a series of planar waveguides in an effort to better understand the diffusion process and to relate the process parameters to the device parameters. The results indicate that it is possible to fabricate highly multimode waveguides which exhibit no fabrication-induced surface defects and no coloration due to silver reduction provided the silver film is not depleted during the diffusion process and the diffusion temperature is low (275°C or less). In addition, scanning electron microscope (SEM) analysis and optical characterization indicate that the maximum index change in the waveguide is strongly dependent on the applied field. We demonstrate that
\Delta n
varies from approximately 0 to 0.075 for fields ranging from 0 to 15 V/mm, making this technique specially attractive for the fabrication of waveguide structures requiring a large, variable change in refractive index.