Comparative study of Ag-Na thermal and field-assisted ion exchange on Er-doped phosphate glass

Silver-sodium ion-exchanged waveguides on a new erbium-doped phosphate glas s have been fabricated and characterized. Thermal diffusion and field-assis ted ion exchanges have been investigated and compared. A simple yet effecti ve method to reconstruct the refractive index profile from the measured eff ective indexes, obtained by the in-lines spectroscopy with prism-coupling t echnique, has been successfully adopted. The optical parameters describing the waveguide properties, namely the refractive index variation, the diffus ion coefficient and, for the field-assisted ion exchanges, the drift veloci ty, have been calculated and correlated with the fabrication parameters. Th ermal diffusion is more reproducible while the field-assisted process provi des a step-like index and better confinement by an appropriate control. Str aightforward guidelines have been outlined for choosing appropriate diffusi on time, temperature and melt composition to fabricate active waveguides co mpatible with optical fibers. (C) 2001 Elsevier Science B.V. All rights res erved.