Graded-index profile analysis from M-line, DNS and EDS measurements of glass waveguides produced by K+/Ag+ ion-exchange combinations

Direct near-surface (DNS) and m-line techniques for the measurement of surface refractive index of ion-exchanged waveguides are compared. Measurements are also compared to direct investigation of ion concentration profiles by energy dispersion spectroscopy (EDS). Good agreement is obtained for the Ag+, K+, and Ag++K+ exchanged samples, but not for the K++Ag+ sample. The index profile approximately follows in a linear proportion the concentration profile after a single Ag+-exchange, while this is not observed for all other samples involving K+-exchange. These results on ion-exchange and refractive-index profiles are discussed, towards a comprehensive and accurate characterization of graded-index waveguides.