Cooperative emission study in ytterbium doped NdVO4

The infrared and visible cooperative emissions of ytterbium ions are studied in Yb-doped NdVO4 single crystals. The absorption of optical phonons allows the emissions at room temperature when a Nd:YAG laser is used. Low temperature emissions are observed due to the Nd3+ -> Yb3+ energy transfer following an argon ion laser excitation of the Nd3+ ions. Analysis of the cooperative emission at low doping concentration (1%) indicates that it is generated by distant pair forming Yb3+ ions while at high doping concentration (>= 5%) close ions magnetically coupled and superexchange mechanisms prevail in the emitting process. (C) 2011 Elsevier B.V. All rights reserved