1 June 1996 Modeling ion exchange in glass with concentration-dependent diffusion coefficients and mobilities
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Optical Engineering, 35(6), (1996). doi:10.1117/1.600727
Abstract
Multimode buried waveguides made in silicate glass by fieldassisted ion exchange present very asymmetric profiles. We show how this phenomenon originates in the large dependence of the kinetics on the local ion concentrations. For this purpose, we derive an interdiffusion equation that includes the effects of concentration-dependent diffusion coefficients and mobilities. We show how to deduce this dependence from measurements on ion-diffused samples. The maximum concentration of the incoming ions is computed from surface equilibrium conditions and is used in the interdiffusion equation as a limiting parameter for coefficient variations. To control the model accuracy for surface as well as buried waveguides, we measure ion profiles with three independent methods: M-lines, scanning electron microscopy, and near-field refractometry. When applied to Ag+-Na+ exchange in silicate glass, the model yields theoretical estimations in good agreement with experiments. This approach underlines the fundamentally nonlinear process that takes place during ion exchange and is also valuable to properly model singlemode waveguide fabrication.
Alexandru I. Lupascu, Antoine P. Kevorkian, Thierry Boudet, Francoise Saint-Andre, Dominique Persegol, Michel Levy, "Modeling ion exchange in glass with concentration-dependent diffusion coefficients and mobilities," Optical Engineering 35(6), (1 June 1996). http://dx.doi.org/10.1117/1.600727
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KEYWORDS
Diffusion

Glasses

Ions

Silver

Ion exchange

Waveguides

Sodium

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