Phonon-mediated temperature dependence of Er³⁺ optical transitions in Er₂O₃

Characterization of the atomic level processes that determine optical transitions in emerging materials is critical to the development of new platforms for classical and quantum networking. Such understanding often emerges from studies of the temperature dependence of the transitions. We report measurements of the temperature dependent Er3+ photoluminescence in single crystal Er2O3 thin films epitaxially grown on Si(111) focused on transitions that involve the closely spaced Stark-split levels. Radiative intensities are compared to a model that includes relevant Stark-split states, single phonon-assisted excitations, and the well-established level population redistribution due to thermalization. This approach, applied to the individual Stark-split states and employing Er2O3 specific single-phonon-assisted excitations, gives good agreement with experiment. This model allows us to demonstrate the difference in the electron-phonon coupling of the S-4(3/2) and H-2(11/2) states of Er3+ in E2O3 and suggests that the temperature dependence of Er3+ emission intensity may vary significantly with small shifts in the wavelength (similar to 0.1 nm) of the excitation source.