Calculation of Judd-Ofelt parameters for Er³⁺ in β-NaYF₄: Yb³⁺, Er³⁺ from emission intensity ratios and diffuse reflectance spectra

We report the calculation of Er³⁺ Judd-Ofelt (JO) parameters for β-phase NaYF₄:Yb³⁺, Er³⁺. The parameters were extracted from measured emission intensity ratios and the diffuse reflectance spectrum, augmented by a single radiative rate constant. The derived parameters were used to calculate the entire suite of radiative rate constants for the f–f transitions of Er³⁺ in the visible and near infrared (NIR) range and to calculate the absorbance spectrum. Two sets of JO parameter values, in units of pm², were calculated using two available sets of reduced matrix elements (Ω₂=2.36, Ω₄=0.22, Ω₆=1.24) and (Ω₂=2.43, Ω₄=0.21, Ω₆=1.22). - Highlights: • We derive Judd-Ofelt (JO) parameters for Er³⁺ doped in a β-NaYF₄ host. • We compare JO parameters derived using two different sets of reduced matrix elements, {U_λ}. • The calculated Einstein A coefficients and emission branching ratios are similar to independently measured quantities. • The calculated relative absorbance spectrum is similar to the measured diffuse reflectance spectrum. • The biggest discrepancies are in transitions involving the ⁴I_9/2 and ⁴F_9/2 states of Er³⁺