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

•Photoluminescence of Er3+ doped and (Er3+-Yb3+) co-doped LiNbO3 (LN) crystals is studied.•Green up-converted luminescence is observed in Er3+ doped LN crystals under 980 nm excitation.•The intensity of the green up-converted luminescence is enhanced in (Er3+, Yb3+) co-doped LN crystals.•An efficient energy transfer between Yb3+ and Er3+ ions in co-doped LN crystals is clearly demonstrated.•Contribution of Er3+-Er3+ pairs and Yb3+-Er3+ pairs are taken into account in a model.

Er3+ doped and (Er3+-Yb3+) co-doped LiNbO3 (LN) crystals grown by the Czochralski method are investigated by photoluminescence spectroscopy. Green up-converted luminescence is observed in Er3+ doped LN crystals under 980 nm excitation. This is explained by an energy transfer between two neighboring Er3+ ions. In (Er3+, Yb3+) co-doped LN crystals, the intensity of the green up-converted luminescence can be further enhanced suggesting that Yb3+ ions also contribute to the up-conversion process. Time resolved photoluminescence measurements clearly demonstrate that an efficient energy transfer occurs between Yb3+ and Er3+ ions. A theoretical model taking into account the contribution of both Er3+-Er3+ pairs and Yb3+-Er3+ pairs is able to describe correctly the decay of the up-converted luminescence.