Infrared-to-visible up-conversion luminescence and energy transfer of RE3+/Yb3+(RE = Ho, Tm) co-doped SrIn2O4

Near-infrared excited up-conversion phosphors of RE3+/Yb3+(RE = Ho, Tm) co-doped SrIn2O4 were synthesized by a solid-state reaction method. X-ray diffraction analysis revealed the phase composition of those samples, and the up-conversion spectroscopic properties were studied in terms of up-conversion emission spectra. Under 980 nm near-infrared laser excitation, strong green emission with the peak at 546 nm was observed in SrIn2O4: Ho3+/Yb3+, which can be assigned to the characteristic 5S2(5F4) → 5I8 transition of Ho3+. Furthermore, SrIn2O4: Tm3+/Yb3+ showed bright blue emission with the peak at 486 nm, which is associated with the 1G4 → 3H6 transition of Tm3+. The UC power studies indicated that the luminescence of SrIn2O4: Ho3+/Yb3+ and SrIn2O4: Tm3+/Yb3+ are attributed to two-photon and three-photon process, respectively. The possible UC luminescence mechanism and energy transfer in SrIn2O4: RE3+/Yb3+ were discussed.