Three different broadband sensitization concepts for optically active erbium ions are reviewed: 1) silicon nanocrystals, with absorption over the full visible spectrum, efficiently couple their excitonic energy to Er3+, 2) silver-related defect states in sodalime silicate glass have absorption in the blue and transfer energy to Er3+, and 3) organic cage complexes coordinated with well-chosen chromophores serve as broadband sensitizers in the visible. Energy transfer rates, efficiencies, and limiting factors are addressed for each of these sensitizers. Implications of the use of strong sensitizers for planar waveguide design are illustrated by using a model for the sensitizing effect of ytterbium.
J. Opt. Soc. Am. B
Photonic Materials

Polman, A., & van Veggel, F. C. J. M. (2004). Broadband sensitizers for erbium-doped planar optical amplifiers: review. J. Opt. Soc. Am. B, 21, 871–892. doi:10.1364/JOSAB.21.000871