Green up-converted luminescence in (Er3+-Yb3+) co-doped LiNbO3 crystals

Abstract Er 3+ doped and (Er 3+ -Yb 3+ ) co-doped LiNbO 3 (LN) crystals grown by the Czochralski method are investigated by photoluminescence spectroscopy. Green up-converted luminescence is observed in Er 3+ doped LN crystals under 980 nm excitation. This is explained by an energy transfer between two neighboring Er 3+ ions. In (Er 3+ , Yb 3+ ) co-doped LN crystals, the intensity of the green up-converted luminescence can be further enhanced suggesting that Yb 3+ ions also contribute to the up-conversion process. Time resolved photoluminescence measurements clearly demonstrate that an efficient energy transfer occurs between Yb 3+ and Er 3+ ions. A theoretical model taking into account the contribution of both Er 3+ -Er 3+ pairs and Yb 3+ -Er 3+ pairs is able to describe correctly the decay of the up-converted luminescence.