Simple approach to calculate the refractive index profile of ion-exchanged waveguides

In graded-index glass waveguides a key factor for the design of components and devices is usually the accurate determination of the refractive index profile as a function of depth. The problem of reconstructing the index profile using the measured effective refractive indices has been faced by several authors. Here we suggest a new expression linear combination of two analitical functions, which is able to provide a good approximation of the solution of the differential equation thath rules the thermal diffusion process. The use of this equation, in connection with the general approach of inverting the Wentzel-Kramer-Bruilloin (WKB) eigenvalue equation, leads to a simple, fast and accurate computation of the refractive index profile obtained by ion exchange.The application of the method to various Ag-echanged waveguides in different glass matrices, with better accuracy than most of the usual procedures, has been demonstrated.