Intense red upconversion emission in infrared excited holmium-doped PbGeO3–PbF2–CdF2 transparent glass ceramic

Intense red upconversion emission around 650 nm in PbGeO3–PbF2–CdF2 transparent glass ceramic containing β-PbF2:Ho3+ nanocrystals, is presented. The holmium-doped vitroceramic samples were excited by a 980 nm diode laser source. The 650 nm upconversion signal was assigned to the 5F5→5I8 transition of holmium ions. Very low intensity signals around 490 and 540 nm corresponding to the 5F2,3→5I8 and 4S2,5F4→5I8 transitions, respectively, were also detected. The upconversion excitation mechanism was achieved through a combination of stepwise phonon-assisted multiphoton absorption, cross-relaxation processes involving pairs of holmium ions, and excited-state absorption. Using a diode laser pump source around 850 nm green upconversion emission around 540 nm was the observed predominant signal.