Determination of oscillator strengths in Pr 3+:YAlO 3 by Raman heterodyne and hole burning spectroscopy

Abstract

The energy separation of several MHz between the nuclear spin substates of rare-earth ions in solids considerably exceeds the homogeneous width of the optical resonance lines, which is typically a few kHz. High-resolution laser experiments like coherent Raman scattering or hole burning experiments, however, can easily resolve optical transitions between individual nuclear spin states. Here, we discuss the calculation and experimental verification of the relative oscillator strengths for all possible transitions between the nuclear spin substates of the 3H 4 ground state and 1D 2 excited state of Pr 3+ : YAlO 3 The oscillator strengths depend on the relative orientation of the quantization axes of the eigenstates in the ground and excited state. We determine the tensor orientation from the orientation dependence of the nuclear magnetic resonance (NMR) spectra, using Raman heterodyne detection and we use spectral hole burning to assign the orientations to the two nonequivalent lattice sites of the Pr 3+ ions in the host lattice.