Mn2 +-sensitized near-IR emission from Nd3 +-activated Sr,Mn-metaphosphate glasses

Abstract

We report on photoluminescence down-shifting and near-IR emission from Nd3+ centers in 50P2O5–(50-x)SrO–xMnO metaphosphate glasses. In those glasses, manganese exists predominantly in its divalent state with a Mn3+ fraction of less than 0.1% of total Mn. The Mn2+ ions are octahedrally coordinated so that a broad red emission band is observed after blue excitation. The emission peak red-shifts from 680 to 743nm, the lifetime decreases from 14.5 to 1.7ms and the internal quantum efficiency decreases from 36.5% to 2.5% with increasing Mn2+ concentration due to concentration quenching, but luminescence activity can still be observed in the pure manganese metaphosphate. The absorption bands of Mn2+ cover the broad region from 300 to 550nm, which allows for the sensitization of Nd3+. Energy transfer from Mn2+ to Nd3+ occurs through a multi-phonon assisted non-radiative down-shifting energy transfer process. A decrease of the emission intensity and lifetime for VIMn2+ is observed after doping with Nd3+ giving evidence for the energy transfer. A value of 89% is estimated for the maximum energy transfer efficiency.