Visible and ultraviolet upconversion emission in LiNbO3 triply doped with Tm3+, Yb3+, and Nd3+

Abstract

Visible and ultraviolet upconversion (UC) emission is observed under 800 nm femtosecond laser excitation in LiNbO3 crystals triply doped with Tm3+, Yb3+, and Nd3+ at room temperature. Energy transfer (ET) from Nd3+ to Yb3+ then to Tm 3+ is very important in this UC emission process. The overlapping between the emissions of 1D2 → 3F 4 and 1G4 → 3H6, which makes up of blue emission band, is confirmed by transient investigation. From the pump energy dependence investigation, it is known that the dominant populating mechanism for the 1G4 state is the two-photon process, and that for 1D2 is the three-photon process. In our UC emission model, the 1G4 state is populated by the ET of 2F5/2(Yb3+)+3H 4(Tm3+) → 2F7/2(Yb 3+) +1G4(Tm3+), 1D 2 state is populated by the ET of 3F2+ 3H4 → 1D2+ 3H 6 among Tm3+ ions. For LiNbO3 crystals doped with Tm3+ to the concentration of 0.9 mol %, the measured lifetimes of 1G4 and 1D2 are ∼ 80 and 4 μs. © 2009 American Institute of Physics.