Blue to NIR down-conversion in Tm3+/Yb3+-codoped fluorozirconate glasses compared to Pr3+/Yb3+ ion-pair

Abstract Visible to near infrared down-conversion has been studied in Tm 3+ /Yb 3+ -codoped fluorozirconate glasses, namely ZBLA (57ZrF 4 -34BaF 2 -5LaF 3 -4AlF 3 in mol%) and ZLAG (70.2ZrF 4 -23.4LaF 3 −0.6AlF 3 -5.8GaF 3 in mol%). Upon blue excitation at 467 nm, Tm 3+ doped glasses yield weak red at 650 nm and strong luminescence around 800 nm. With the addition of Yb3+, emission between 950 and 1100 nm from the Yb 3+ : 2 F 5/2 → 2 F 7/2 transition was observed. This emission well matched with the band gap of crystalline silicium. The mechanism responsible for down-conversion in the Tm 3+ /Yb 3+ ion-pair is a down-shifting process. The highest energy transfer efficiency η ETE was 64.5% in ZBLA glasses doped with 0.75Tm 3+ /10Yb 3+ ; this efficiency was mainly limited by the strong Yb 3+ to Tm 3+ back energy transfer. ηETE appeared to increase more rapidly with the addition of Yb 3+ in ZLAG glasses, as already observed for the energy transfer in Pr 3+ /Yb 3+ ion-pair. The origin of the difference between the two hosts is probably related to the distribution of rare-earth ions in the host matrix, as shown by molecular dynamics simulation. The Tm 3+ /Yb 3+ system is found much less efficient that the Pr 3+ /Yb 3+ one, because of less efficient quantum efficiency together with lower blue absorption of Tm 3+ compared to Pr 3+ .