Raman heterodyne interference: Symmetry analysis

The Raman heterodyne interference phenomenon observed recently in the impurity-ion crystals Pr3+ and Pr3+ is examined from the viewpoint of symmetry analysis of the nonlinear susceptibility tensor. General Raman heterodyne signals are derived for all crystal symmetries and for all optical-frequency and radiofrequency polarizations. An example of the utility of this approach resolves a controversy over the crystal symmetry of LaF3, establishing that it is trigonal rather than hexagonal. © 1985 The American Physical Society.