Multiphonon assisted upconversion violet emissions of Er3+high-lying excited Stark sub-levels in Er3+-Yb3+co-doped YAG transparent ceramics

Luminescence from high-lying excited states, such as the²G9/2level of Er³⁺, has been rarely explored due to its low population and complex excitation mechanisms. However, such luminescence carries important information of high-lying excited states, and hence offers a unique probe for understanding temperature-driven dynamics and phonon-mediated processes in luminescence upconversion systems. Herein, we report temperature-dependent upconversion photoluminescence measurements of Er³⁺in Er³⁺-Yb³⁺co-doped transparent ceramics, with a particular focus on transitions involving closely spaced Stark-split sub-levels in the violet emission band. Two excitation pathways are employed to investigate the thermal behavior mediated by phonons. The observed negative thermal quenching phenomenon under 980 nm excitation is well described through a rate-equation-based model that includes thermally coupled Stark sub-levels, phonon-assisted optical excitations and multi-phonon nonradiative relaxation. These insights into the phonon-assisted population dynamics provide a physical basis for the future development of optical thermometric applications.

Duke Scholars

Author Changcheng Zheng DKU Faculty