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International audience; Rare earth doped nanocrystals have been recently suggested as useful materials for applications in quantum information processing. To reach optical properties closer to bulk crystals ones, it is still necessary to reduce the defects that can arise in nanoscale structures. Here, we probe the defects level by monitoring the inhomogeneous broadening of the 7 F 0  5 D 0 transition in particles of 0.3% Eu 3+ :Y 2 O 3. We find that lines as narrow as 14 GHz (0.015 nm), a value comparable to single crystals, can be obtained in 150 nm particles calcinated at 1200°C. The additional broadening observed for particles calcinated at lower temperature is attributed to defects inside crystallites and not to surface effects. A linear correlation is also observed between optical and Raman linewidths, suggesting that both processes are sensitive to the same defects. 5 D 0 excited state lifetimes are well described by a model based on an effective refractive index and we conclude that the defects causing the inhomogeneous broadening have no effect on the excited state population.

We present results of the theoretical study of optical characteristics for the small-radius optical centers in the subwavelength ellipsoidal nanocrystals embedded in a medium. Analytical expressions are obtained for the electric-dipole and magnetic-dipole decay rates of excitations of optical centers in a magnetodielectric nanocomposite.

We report for the first time how the optical transitions associated with a localized impurity can be modulated by quantum confinement. The effect of quantum confinement on an impurity critically depends on the size of the host nanocrystal. The luminescent properties of Y 2 O 3 : Tb 3+ and ZnS : Mn 2+ are discussed within the framework of the quantum-confined atoms.

The properties and applications of nanocrystals doped with transition and rare-earth impurities are reviewed. The high efficiency and ultrafast recombination times observed in these doped nanocrystals make these materials very attractive for optoelectronic applications.

The role of transition and rare-earth impurities in a quantum dot is discussed. The high efficiencies observed in these doped nanocrystal materials make them very attractive for optoelectronic applications.