Modeling and interference-microscopy characterization of graded index transitions in ion-exchange waveguide integrated elements: transitions between annealed surfaces

We employ interference microscopy to characterize in a direct and local way the graded index transitions at the boundaries of integrated optical eleme nts fabricated by multistep ion-exchange processes, a task not yet possible by other technologies. A particular fabrication method based on purely the rmal ion-exchange, which allows local single-mode propagation, is investiga ted. The refractive-index distribution is modeled on the basis of the linea r theory of diffusion and adiabatic transitions of the refractive-index pro file. Finally, its validity is analyzed by microinterferometry.