Physical review. B, Condensed matter
Static and dynamic contributions to the lowest 4f→5dtwo-photon transition in CaF2 : Ce3+
R C Leavitt
Abstract
A theoretical analysis of the lowest zero-phonon 4f\ensuremath{\rightarrow}5d two-photon absorption cross section in ${\mathrm{CaF}}_{2}$:${\mathrm{Ce}}^{3+}$ is presented. The transition is parity allowed because of an interaction of the rare-earth ion with the odd-parity components of the crystal field. This interaction takes two forms. The static contribution serves to mix the 4f and 5d orbitals, while a dynamic term couples the rare-earth orbitals to the nearby ligand states. A comparison of the predicted polarization anisotropy to the experimentally measured value allows an estimate of the relative strengths of the static and dynamic terms. The theoretical estimates of both the polarization anisotropy and the absolute magnitude of the cross section compare well with the experimental results.