Investigation of Refractive-index Profiles of Ion-exchanged Planar Waveguides in Glass

Abstract

New data concerning the refractive-index profiles in Ag/Na ion-exchanged waveguides are obtained using a parabolic-segment reconstruction method. The profiles can be described as second-order polynomials, but with a mean curvature b = 2·8 which is significantly greater than the originally suggested value 0·64. The profile so obtained agrees very well with the common diffusion equation for the silver ion concentration only if one assumes a simple linear relationship between the diffusion coefficient and the concentration. This fact necessitates changes in present ideas about the ion-exchange mechanism in sodalime glasses.