Near-infrared to green photon upconversion in Mn2+ and Yb3+ doped lattices

Yb3+ excitation in the near-infrared around 1 μm leads to green Mn2+ 4T1 → 6A1 luminescence in CaZnF4:Mn2+; Yb3+, Zn2SiO4:Mn2+; Yb3+ and SrZnCl4:Mn2+; Yb3+ at 15 K. In the former two compounds the green upconversion (UC) luminescence is visible by eye up to room temperature. In Cs3MnBr5:Mn2+; Yb3+ no UC luminescence is observed. The UC mechanism consists of a sequence of ground-state absorption and excited-state absorption steps. The UC efficiency at 15 K is of the order of 1% for laser excitation with 130 mW (f=53 mm focusing lens).