The optical transmission spectra of glasses are shown in Fig. 1.
Increase in the concentration of cerium ions leads to a slight red-
shift of the transmission edge (Fig. 1a). In the visible region the
samples are transparent, i.e. the transmission coefficient is about
90%. Similar shift is observed in oxyfluoride aluminosilicate glasses
[11] and phosphate fluoride glasses [12]. This phenomenon is
associated with interconfiguration transitions in Ce 3þ 4f -5d ion.
In the sample with the cerium concentration of 0.2 wt%, weak
absorption peaks with maxima at 350, 367, 378 and 485 nm are
recorded in the transmission spectrum which are apparently