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Photoluminescence of Ho3+ :YVO4 crystals
No full textEmission spectra of Ho3+-doped YVO4 crystals are studied in the visible and infrared spectral regions. Be3+ sides the emission bands at 544 nm and at about 1950 and 2017 nm due to Ho, we observed a broad emission band at 6 10 nm at low temperatures like 15 K in the highly doped crystals with the Ho3+ concentrations of more than 0.5 mol %. The excitation band for this broad emission is located at 390 nm which is near the edge of band gap of the crystal. It is suggested that the 610 nm band is attributed to defects related to oxygen vacancies around V4+ ions. (c) 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Cooperative emission study in ytterbium doped NdVO4
No full textThe 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
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