Spectroscopic investigations of multiple environments in Er: CaWO4 through charge imbalance

We present a detailed spectroscopic study of the I13/24 and I15/24Er3+ multiplets of Er:CaWO4 grown without a co-dopant. Using photoluminescence and photoluminescence excitation measurements, we find multiple environments into which erbium ions are incorporated in the crystal. For the four most prevalent environments, we provide a complete assignment of the I13/24 and I15/24 sublevel energies. Polarization-dependent absorption and emission spectroscopy allow us to identify the irreducible representations of the states and determine the dipole nature of transitions. In addition, we compare the different relaxation paths within I13/24 and I15/24 multiplets via line broadening and lifetime measurements. Finally, spectral, lifetime, and polarization measurements indicate similarities between the studied environments. Published by the American Physical Society 2025