Knowledge Bank

Results are presented of a far infrared interferometric research program to assess the potential use as host materials for solid state lasers of those rare earth trifluorides crystallizing in the tysonite structure. Kramers-Kronig analyses of the polarized lattice-vibrational reflection spectra of $LaF3,CeF3,PrF3$ and $NdF3$, taken as a close function of temperature between $5\circ$ and $600\circ K$, have led to an assignment of the crystal symmetry of the tysonite structure and have provided an assessment of the strength of non-linear interactions in these materials.