Dependence of refractive index on silver concentration in gradient-index glass

The Huggins, Sun and Davis model is widely used in the field of gradient-index optical imaging systems for predicting refractive index distributions from composition data of diffused glasses. This model is tested in five silver-doped gradient-index glass samples with changes in refractive index up to 0.09 at 0.06471 μm and distribution depths up to 3.3 mm. Index profiles are measured interferometrically. Absolute concentration profiles are measured using energy dispersive x-ray spectroscopy. The data show that the HSD model is valid only for dopant levels below one mol% in silver-diffused glasses. Reasons for departure from the model are suggested.