Figure 4.

Total absorption coefficient at 452 nm versus Dy${}^{3+}$ content for Dy${}^{3+}$ (full circles) and Tb${}^{3+}$ (full triangles) single-doped as well as Dy${}^{3+}$/Tb${}^{3+}$ (full squares) double-doped BaB glasses. The solid line represents a least squares fitting to the experimental data. The glass background is indicated by the dashed line.