Absorption intensities, emission cross sections, and crystal field analysis of selected intermanifold transitions of Ho3+ in Ho3+:Y2O3 nanocrystals

Optical absorption and emission intensities are investigated for Ho3+ in nanocrystalline Ho3+:Y2O3. Room temperature absorption intensities of Ho3+(4f(10)) transitions in synthesized Ho3+:Y2O3 nanocrystals have been analyzed using the Judd-Ofelt (JO) approach to obtain the phenomenological intensity parameters Omega(2), Omega(4), and Omega(6). The JO intensity parameters are used to calculate the spontaneous emission probabilities, radiative lifetimes, and branching ratios of the Ho3+ transitions from the upper multiplet manifolds to the corresponding lower-lying multiplet manifolds L-2S+1(J) of Ho3+ (4f(10)). The emission cross sections of the intermanifold transitions F-5(4), S-5(2) --> I-5(8) (0.549 mu m) and I-5(6) --> I-5(8) (1.204 mu m) have been determined. The room temperature fluorescence lifetimes of these transitions in Ho-3+:Y2O3 nanocrystals were measured. Radiative and fluorescence lifetimes are used to determine the quantum efficiency. The low temperature spectra are analyzed for the energy (Stark) level transitions of select L-2S+1(J) multiplet manifolds of Ho3+(4f(10)). The comparative study of Ho3+(4f(10)) ions suggests that synthesized Ho3+: Y2O3 nanocrystals could be an excellent alternative to single-crystal Ho3+:Y2O3 for certain photonic applications, especially in the near infrared region. (C) 2009 American Institute of Physics. [doi:10.1063/1.3211298]