On the Er3+ NIR photoluminescence at 800 nm

Here, we study the Er3+ NIR I-4(9/2)-I-4(15/2) photoluminescence peaking at 8(X) nm. It can be detected with a good signal-to-noise for the prepared CaWO4:Yb3+,Er3+ phosphors upon excitation at 980 nm. When directly exciting the Er3+ green and red emitting states over the 333-773 K temperature range, the 800 nm photoluminescence for the samples is undetectable. It shows that the non-radiative relaxation from the upper excited states to the I-4(9/2) emitting state is extremely inefficient. Moreover, the 800 nm photoluminescence decay curve is measured at high temperatures. It is found that the 800 nm emission always has a similar lifetime with the Er3+ I-4(11/2)-I-4(15/2) transition. This reminds us that the Er3+ 4I9/2 state is mainly populated by the adjacent lower I-4(11/2) state by a thermally coupled way. (C) 2020 Optical Society of America under the terms of the OSA Open Access Publishing Agreement