Spectroscopic Analysis of Nd$^{3+}$:Y$_{2}$O$_{3}$ Nanocrystals in Polymers and Copolymers

Spectroscopic properties of nanocrystalline Nd$^{3+}$ in Nd$^{3+}$:Y$_{2}$O$_{3 }$embedded in solid plastic hosts (2-hydroxyethyl methacrylate (HEMA) and copolymer of HEMA/styrene) are characterized. The standard Judd-Ofelt model has been applied to the room temperature absorption intensities of Nd$^{3+}$(4$f^{3})$ transitions in the plastic hosts to determine the three phenomenological intensity parameters: \textit{$\Omega $}$_{2}$, \textit{$\Omega $}$_{4}$, and \textit{$\Omega $}$_{6}$. Intensity parameters are then utilized to determine the radiative decay rates and branching ratios of the Nd$^{3+}$(4$f^{ 3})$ transitions from the upper manifold state $^{4}F_{3/2}$ to the lower-lying multiplet manifolds $^{4}I_{J }$(J= 9/2, 11/2, 13/2, 15/2). Emission cross sections and room temperature fluorescence lifetimes of the important intermanifold $^{4}F_{3/2} \quad \to \quad ^{4}I_{J }$(J=9/2, 11/2, 13/2)$_{ }$transitions are determined. We investigate the detailed crystal-field splitting of the energy levels of the Nd$^{3+ }$ion in the Y$_{2}$O$_{3}$/polymer host. The 300 K spectra$_{ }$are analyzed for the energy level transitions between the $^{2S+1}L_{J}$ multiplet manifolds of Nd$^{3+}$(4$f^{3})$. Results are also compared with a crystal-field splitting analysis reported earlier for single-crystal Nd$^{3+}$:Y$_{2}$O$_{3}$.