PROPRIÉTÉS OPTIQUES DU FLUOROGERMANATE ET DE L'ARSÉNIATE DE MAGNÉSIUM EXCITÉS PAR L'ULTRAVIOLET DE COURTE LONGUEUR D'ONDE

On a étudié les spectres d'émission et d'excitation du fluorogermanate et de l'arséniate de magnésium activés au manganèse en irradiant les produits par l'ultraviolet de longueur d'onde comprise entre 800 et 2 900 Å et on a déterminé les rendements quantiques de fluorescence correspondants.Emission and excitation spectra were studied and the quantum yield was determined for manganese activated magnesium fluorogermanate and arsenate. The measurements were carried out in the range from 800 to 2 900 Å

Photonic Effects on the Radiative Decay Rate and Luminescence Quantum Yield of Doped Nanocrystals

Nanocrystals (NCs) doped with luminescent ions form an emerging class of materials. In contrast to excitonic transitions in semiconductor NCs, the optical transitions are localized and not affected by quantum confinement. The radiative decay rates of the dopant emission in NCs are nevertheless different from their bulk analogues due to photonic effects, and also the luminescence quantum yield (QY, important for applications) is affected. In the past, different theoretical models have been proposed to describe the photonic effects for dopant emission in NCs, with little experimental validation. In this work we investigate the photonic effects on the radiative decay rate of luminescent doped NCs using 4 nm LaPO4 NCs doped with Ce3þ or Tb3þ ions in different refractive index solvents and bulk crystals. We demonstrate that the measured influence of the refractive index on the radiative decay rate of the Ce3þ emission, having near unity QY, is in excellent agreement with the theoretical nanocrystal-cavity model. Furthermore, we show how the nanocrystal-cavity model can be used to quantify the nonunity QY of Tb3þ-doped LaPO4 NCs and demonstrate that, as a general rule, the QY is higher in media with higher refractive index