Optical Materials (2011)

Resonance modes in rare earth doped microcrystals
Katleen Korthout, Philippe F. Smet, Dirk Poelman
Optical Materials 33 (2011) 1128-1130

Abstract
Alkaline earth sulfide phosphors doped with Eu2+ or Ce3+ are good candidates for wavelength conversion in LEDs for general lighting applications. A very broad emission spectrum can be obtained by preparing SrS:Eu|SrS:Ce core|shell particles. These microcrystals are rectangular cuboids and can also be efficiently excited with electrons in a scanning electron microscope. The broad emission spectrum, ranging from 450 nm to 650 nm, consists of the combined emission of Ce3+ and Eu2+ centers. Using cathodoluminescence (CL) in a scanning electron microscope, evaluation of the emission characteristics of individual cuboids was possible. Sharp peaks in the CL-spectra of individual particles could be observed and described as being resonance modes. The spectral positions and the line widths of resonance modes in these core|shell microcrystals are predicted by an extension of the plane wave model, taking into account the dispersion of the refractive index and the existence of open orbits.

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