Intensity analysis and energy-level modeling of Nd$^{3+}$ in Nd$^{3+}$:Y$_{2}$O$_{3}$ nanocrystals in polymeric hosts

Optical absorption and emission intensities are investigated for Nd$^{3+}$ in nanocrystalline Nd$^{3+:}$Y$_{2}$O$_{3}$. Room temperature absorption intensities of Nd$^{3+}$(4$f^{3})$ transitions in synthesized Nd$^{3+:}$Y$_{2}$O$_{3 }$nanocrystals have been analyzed using the Judd-Ofelt (J-O) approach to obtain the phenomenological intensity parameters. The J-O intensity parameters are used to calculate the spontaneous emission probabilities, radiative lifetimes, and branching ratios of the Nd$^{3+}_{ }$transitions from the upper multiplet manifolds to the corresponding lower-lying multiplet manifolds $^{2S+1}L_{J}$ of Nd$^{3+}$(4$f^{3})$. The emission cross sections and room temperature fluorescence lifetimes of the important intermanifold $^{4}F_{3/2} \quad \to $ $^{4}I_{J }$(J=9/2, 11/2, 13/2, 15/2)$_{ }$transitions have been determined. We also compare the spectra of the Nd$^{3+}$:Y$_{2}$O$_{3}$ nanocrystals to those of the nanocrystals embedded in polymeric matrices of epoxy and chitosan, and we find similarities in terms of the detailed Stark energy levels of the Nd$^{3+ }$ion in the Y$_{2}$O$_{3}$ nanocrystalline host. The 300 K spectra$_{ }$are analyzed for the energy (Stark) level transitions between the $^{2S+1}L_{J}$ multiplet manifolds of Nd$^{3+}$(4$f^{3})$. The results of this study are also compared with a crystal-field splitting analysis reported earlier for single-crystal Nd$^{3+}$:Y$_{2}$O$_{3}$ grown by a modified flame fusion method.