Multiphoton ultraviolet and visible upconversion luminescence of Tm3+Yb3+ co-doped oxyfluoride glass

The ultraviolet upconversion luminescence of Tm3+ ions sensitized by Yb3+ ions in oxyfluoride glass when excited by a 975 nm diode laser was studied in this paper. One typical ultraviolet upconversion luminescence lines positioned at 362.3 nm was found. It can be attributed to the five-photon upconversion luminescence transition of D-1(2) -> H-3(6). Several visible upconversion luminescence lines at 451.1 nm, (477.9 nm, 462.5 nm), 648.7 nm, (680.5 nm, 699.5 nm) and (777.5 nm, 800.7 nm) were found also, which results from the fluorescence transitions of five-photon D-1(2) -> F-3(4), three-photon (1)G(4) -> H-3(6), three-photon (1)G(4) -> F-3(4), two-photon F-3(3) -> H-3(6) and two-photon H-3(4) -> H-3(6) of TM3+ ion, respectively. The theoretical analysis suggests that the upconversion mechanism of the 362.3 nm D-1(2) -> H-3(6) upconversion luminescence is the cross energy transfer of {H-3(4)(TM3+) -> F-3(4)(TM3+), (1)G(4)(TM3+), D-1(2)(TM3+)} and {(1)G(4)(Tm3+) -> F-3(4)(Tm3+), H-3(4)(TM3+) -> D-1(2)(TM3+)} between TM3+ ions. In addition, the upconversion luminescence of (1)G(4) and H-3(4) state results from the sequential energy transfer {F-2(5/2)(Yb3+) -> F-2(7/2)(Yb3+), H-3(4)(TM3+), (1)G(4)(TM3+)} and {F-2(5/2)(Yb3+) -> (2)F7/2 (Yb3+), F-3(4)(TM3+), F-3(2)(TM3+)} from Yb3+ ions to TM3+ ions, respectively. (c) 2007 Published by Elsevier B.V.