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

摘要

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 botained 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.