Optical Transitions and Excited State Absorption Cross Sections of SrLaGaO₄ Doped with Ho³⁺ Ions

The spectroscopic properties of SrLaGaO₄ (SLO) crystal doped with Ho³⁺ ions were studied in this work. Absorption, emission spectra and decay dynamics of excited states have been measured and discussed using the Judd-Ofelt model. Photoluminescence emissions were attributed to transitions from the excited ³D₃, ⁵S₂, ⁵F₅, ⁵I₆ and ⁵I₇ multiplet manifolds. The experimental lifetimes for five excited states have been compared to the theoretical values, calculated using Judd-Ofelt theory, allowing for the determination of the multiphonon relaxation rates (W_nR) of the respective states. The experimental data were approximately on a line expressed by W_nR = W₀ exp(-αΔE) with W₀ = 0.5 × 10⁷ s^-1 and α = 2.6 × 10^-3 cm. To discuss the excited state absorption (ESA) pathways, that originated from several excited levels, we used the Judd-Ofelt formalism allowing determination of the integrated cross section for ESA transitions.