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Abstract
Simulations of coherent phonon-polaritons in ferroelectric crystals have been performed to guide impulsive stimulated Raman scattering (ISRS) characterization of lattice anharmonicity. ISRS excitation of the polar ferroelectric mode and propagation of phonon-polaritons in two spatial dimensions within the crystal are examined. The correct relation between the light scattering and phonon-polariton wavevectors is derived. Using model anharmonic potentials, we find that harmonics of the polariton wavevector, rather than harmonics of the polariton frequency, are key signatures of lattice anharmonicity. This suggests an experimental refinement, which we call time-resolved wavevector overtone spectroscopy, for observation of lattice anharmonicity.