'Er POT.3+' -doped germanate glasses for active waveguides prepared by 'Ag POT.+'/'K POT.+'<--> 'Na POT.+' ion-exchange - Barbosa, A. J.; Maia, L. J. Q.; Nascimento, A. M.; Gonçalves, Rogéria Rocha; Poirier, G.; Messaddeq, Y.; Ribeiro, S. J. L. (Journal of Non-Crystalline Solids, 2008)