Analyses of ion-exchanged glass optical waveguides by means of secondary ion mass spectroscopy: Condensation of impurity halide ions at the surface

We analyzed the chemical composition of K+-exchanged glass optical waveguides (OWGs) by secondary ion mass spectroscopy. Extensive condensation of impurity halide ions took place at the surface of the OWGs in the ion-exchanging and annealing processes. The condensation of Cl- ions is likely a cause of the abnormal behavior observed for soda-lime glass OWGs; that is, a guided mode having appeared during the annealing did not disappear even after long annealing. Moreover, it was suggested that a space charge layer was formed at the OWG surfaces owing to the condensation of the halide ions.