Characterization and modeling of planar surface and buried glass waveguides made by field-assisted K(+) ion exchange

Planar, surface, and buried optical waveguides were fabricated by using an electric field-assisted K(+) ion exchange in soda-lime glass. The refractive-index (concentration) profiles were determined by using scanning electron microscopy and mode-index measurements. These profiles were theoretically modeled by solving the diffusion equation numerically and correlated well with the scanning electron microscopy measurements. For single-mode surface waveguides, mode-index measurements were made to establish the effective guide depth and migration velocity, given the electric field, the temperature, and the time. The migration velocity was found to be different from that for the multimode case. For buried waveguides the profile was modeled by a modified buried Fermi distribution whose fitting parameters were determined for the given fabrication conditions.