Multiphoton ultraviolet and visible upconversion luminescence of Tm 3+Yb 3+ co-doped oxyfluoride glass

Abstract

The ultraviolet upconversion luminescence of Tm 3+ ions sensitized by Yb 3+ 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 1D 2 → 3H 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 1D 2 → 3F 4, three-photon 1G 4 → 3H 6, three-photon 1G 4 → 3F 4, two-photon 3F 3 → 3H 6 and two-photon 3H 4 → 3H 6 of Tm 3+ ion, respectively. The theoretical analysis suggests that the upconversion mechanism of the 362.3 nm 1D 2 → 3H 6 upconversion luminescence is the cross energy transfer of { 3H 4(Tm 3+) → 3F 4(Tm 3+), 1G 4(Tm 3+) → 1D 2(Tm 3+)} and { 1G 4(Tm 3+) → 3F 4(Tm 3+), 3H 4(Tm 3+) → 1D 2(Tm 3+)} between Tm 3+ ions. In addition, the upconversion luminescence of 1G 4 and 3H 4 state results from the sequential energy transfer { 2F 5/2(Yb 3+) → 2F 7/2(Yb 3+), 3H 4(Tm 3+) → 1G 4(Tm 3+)} and { 2F 5/2(Yb 3+) → 2F 7/2(Yb 3+), 3F 4(Tm 3+) → 3F 2(Tm 3+)} from Yb 3+ ions to Tm 3+ions, respectively.