Energy transfer in Dy/Tb double-doped borate glass for blue-to-green conversion

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.