Temperature-dependent photoluminescence spectra of Er–Tm-codoped Al 2O 3 thin film

Abstract

Er–Tm-codoped Al 2O 3 thin films with different Tm to Er concentration ratios were synthesized by cosputtering from separated Er, Tm, Si, and Al 2O 3 targets. The temperature dependence of photoluminescence (PL) spectra was studied. A flat and broad emission band was achieved in the 1.4–1.7 μm and the observed 1470, 1533 and 1800 nm emission bands were attributed to the transitions of Tm 3+: 3H 4 → 3F 4, Er 3+: 4I 13/2 → 4I 15/2 and Tm 3+: 3F 4 → 3H 6, respectively. The temperature dependence is rather complicated. With increasing measuring temperature, the peak intensity related to Er 3+ ions increases by a factor of five, while the Tm 3+ PL intensity at 1800 nm decreases by one order of magnitude. This phenomenon is attributed to a complicated energy transfer (ET) processes involving both Er 3+ and Tm 3+ and increase of phonon-assisted ET rate with temperature as well. It should be helpful to fully understand ET processes between Er and Tm and achieve flat and broad emission band at different operating temperatures.