Optical coherence and hyperfine structure of the F07↔5D0 transition in Eu3+:CaWO4

Abstract

Rare-earth ions doped in crystals with low nuclear-spin densities are highly promising candidates for quantum technology applications. In this study, we investigated the spectroscopic properties of the ${}^{7}F_0{\leftrightarrow }^5{D}_0$ optical and the hyperfine transitions of $E{u}^{3+}$ ions in a CaWO₄ crystal, where the nuclear spin arises solely from the ${}^{183}W$ isotope, with a natural abundance of 14%. At a temperature of 3 K, we experimentally identified four distinct crystal field environments for $E{u}^{3+}$ ions in a 0.1 at.% $E{u}^{3+}$ doped CaWO₄ crystal. The optical coherence properties of Eu³⁺ ions in these environments were characterized. Additionally, we resolved the hyperfine structures in the ${}^{7}F_0$ ground state and ${}^{5}D_0$ excited state, and determined the ${}^{7}F_0$ ground state lifetimes using spectral hole burning techniques. These findings highlight the significant potential of $E{u}^{3+}$:$\mathrm{CaW}{O}_4$ for optical quantum memory applications.