Dy \(^{3+}\) single- and Dy \(^{3+}\) /Tb \(^{3+}\) double-doped LiAlB and BaB glasses are investigated for their external quantum efficiency under 452-nm excitation. In the case of double-doping, the energy transfer from Dy \(^{3+}\) to Tb \(^{3+}\) results in a combination of both Dy \(^{3+}\) - and Tb \(^{3+}\) -related emissions though Tb \(^{3+}\) cannot be excited directly at 452 nm. The energy transfer efficiency is obtained by deconvolution of the photoluminescence spectrum into the corresponding Dy \(^{3+}\) and Tb \(^{3+}\) components. There is, however, also an energy transfer from Tb \(^{3+}\) to Dy \(^{3+}\) which is confirmed by lifetime measurements.
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