New insight into two-step near-infrared quantum cutting in Pr^3+ singly doped oxyfluoride glass-ceramics

Efficient near-infrared (NIR) quantum cutting (QC) in RE3+/Yb3+ requires the UV-blue photon excited RE3+ donor has intermediate energy level to separate the energy gaps (~10000 cm−1) resonant to Yb3+absorption. Thus the unique Pr3+/Yb3+ resonant QC at low Yb3+content (room temperature) essentially requires Pr3+-doping features distinctive NIR radiative transitions: in our prepared Pr3+-doped oxyfluoride glass-ceramics containing CaF2 nanocrystals, a two-photon NIR-QC from blue-photon excited 3Pj (j = 0, 1, 2) states takes place efficiently with 1G4 acting as an intermediate level. The underlying energy transfer mechanisms involving the two-step sequential transitions of 3P0→1G4 ~915 nm and 1G4→3H4 ~990 nm (crucial resonant routes for the further 1Pr3+→2Yb3+), as well as the 1D2→3F2 ~873 nm and 1D2→3F3,4 ~1040 nm, are rationally distinguished by means of photoemission, excitation, and time-resolved fluorescence spectra.