A Raman heterodyne study of the hyperfine interaction of the optically-excited state 5D0 of Eu3+:Y2SiO5

The ground-state spin coherence time of 151Eu3+ in Y2SiO5 crystal in a critical magnetic field was extended to six hours in a recent work [Zhong et al. Nature 517, 177 (2015)], which paved the way for constructing quantum memory with long storage time. In order to select a three-level system for quantum memory applications, information about the excited-state energy level structures is required for optical pumping. In this work, we experimentally characterize the hyperfine interaction of the optically-excited state 5D0 using Raman heterodyne detection of nuclear magnetic resonance (NMR). The NMR spectra collected in 201 magnetic fields are well fitted. The results can be used to predict the energy level structures in any given magnetic field, thus enabling the design of optical pumping and three-level quantum memory in that field.