Pr^3+ cluster management in CaF_2 by codoping with Lu^3+ or Yb^3+ for visible lasers and quantum down-converters

The codoping of CaF2:Pr3+ with Yb3+ or Lu3+ ions is shown to avoid the clustering of Pr3+ ions, which otherwise prevent Pr3+ doped CaF2 to be used for various photonic applications. The breaking of Pr3+ clusters by Lu3+ ions paves the way towards the development of a Pr3+ doped CaF2 visible laser. On the other hand, the formation of Pr3+-Yb3+ clusters in place of Pr3+ clusters leads to extremely efficient energy transfers between Pr3+ and Yb3+ which could be used for quantum cutting applications. Two types of clusters are observed for both types of codopings. Pr3+ to Yb3+ energy transfer analysis shows that for one of the clusters an ultrafast energy transfer takes place with a rate of 5×107  s−1, which is likely due to exchange interaction.