Upconversion spectroscopy of Al2O3:Er3+

The spectroscopic properties of Al2O3:Er3+ thin films have been investigated by lifetime measurements. The luminescence decay curves show an initial non-exponential component, followed by an exponential tail, whose decay time decreases with increasing Er3+ concentration. This behavior can be described with good accuracy by a microscopic treatment that takes into account both energy migration and energy-transfer upconversion among Er3+ ions. Parameters such as the migration mean time τ0 and the donor-acceptor transfer probability CDA are derived. We show that, in the concentration range of interest for waveguide amplifiers at 1.5 µm, upconversion occurs mostly in the static regime