A spectroscopic investigation of sodium–zinc–aluminosilicate glasses activated with Sm 3+ and Tb 3+ /Sm 3+ ions is performed through their luminescence spectra and decay times. Yellowish-green light emission, with x=0.37 and y=0.58 CIE chromaticity coordinates, is obtained in the Tb 3+ /Sm 3+ codoped glass excited at 318nm. Such yellowish-green emission is generated by the simultaneous emission of Tb 3+ and Sm 3+ ions, samarium being sensitized by the terbium through a non-radiative energy transfer. From spectroscopic data it is inferred that this energy transfer takes place between Tb 3+ and Sm 3+ clusters through a short-range interaction mechanism. Optical waveguides are also effectively produced in the glasses by Ag + –Na + ion exchange.