Influence of annealing on the diffusion characteristics and optical losses of multimode Ag +-glass waveguides

Abstract

In the recent paper the experimental investigation of changes of optical and diffusion characteristics of multimode Ag +-glass waveguides in the process of annealing is presented. It has been shown that the process of refractive index profile redistribution in investigated samples had irregular and step-by-step character. At first the refractive index in the underlying waveguide layers increased because of a silver ions outflow from near-surface regions. Then silver ions started to migrate all over the waveguide profile and finally the silver ion concentration did not vary significantly in the medium layers of waveguide but the waveguide length kept growing. The refractive index profile redistribution was accompanied by change of waveguide mode losses. Experimental results let us conclude that major sources of optical losses were the microscopic metallic conglomerates in the waveguide region. During annealing their concentration in the near surface region decreased at first and then increased while in the underlying regions their concentration practically did not change. The space and temporal dependences of diffusion coefficients of the ion-exchanged process of silver ions in glass have been obtained in the result of the inverse diffusion problem solution. The maximum value of the diffusion coefficient was about 2.73×10 −15 m 2/ s .