Synthesis and optical properties of infrared-emitting _YF3:Nd nanoparticles

Nd3+ -doped YF3 (YF3:Nd) nanoparticles with a size of ∼20 nm were synthesized by solvothermal decomposition of yttrium and neodymium trifluoroacetate precursors in oleylamine. Using the 4f -energy matrix diagonalization procedure various interaction parameters: Slater-Condon (F ₂, F₄, and F₆), spin-orbit (), two body interaction (α, Β, and γ), Judd parameters (T₂, T₃, T₄, T₆, T₇, and T₈), spin-other-orbit parameters (M₀, M₂, and M₄) and electrostatically correlated spin-orbit interaction parameters (P ₂, P₄, and P₆), and the crystal-field parameters (B_qk) were evaluated. The potential of YF3:Nd as a laser host for 1052 nm emission was evaluated by quantitative analysis of the absorption, emission spectra, and fluorescence decay characteristics. Judd-Ofelt parametrization was employed to compute the radiative spectral parameters such as radiative transition probabilities, fluorescence branching ratios, stimulated emission cross sections, and quantum efficiencies of the observed bands in the fluorescence spectrum. Using the measured radiative properties, 75% quantum efficiency was obtained for the principal emission band at 1052 nm when the Nd dopant concentration was 0.25 mol%, with an emission cross section of 0.74× 10-20 cm2. Analysis of the energy transfer kinetics showed that at low dopant concentrations of 0.25 mol% dipole-dipole interactions were dominant, whereas energy migration was the leading process at higher dopant concentrations. Quenching by OH impurities was found to be within the limit of optimum amplifier performance where multiphonon relaxation losses were negligible. Preliminary optical characterization showed that these nanocrystalline materials can be potentially used as optical amplifiers and in applications like infrared imaging, security and authentication.