Time-resolved three-color coherent raman scattering applied to polycrystalline and opaque solids

A new time-resolved coherent Raman technique (three-color picosecond coherent anti-Stokes Raman scattering), which uses a backscattering geometry and three colors obtained from three different lasers, is demonstrated. The advantage of this technique over conventional two-color picosecond coherent anti-Stokes Raman scattering is that it is insensitive to sample morphology. It is used to study time-dependent vibrational dephasing from opaque, polycrystalline solids at low temperature. A quantitative treatment of the limiting apparatus time response, where each pulse has a different duration and where there is arrival-time jitter between the pulses, is derived. New measurements of vibrational dynamics in low-temperature carbon disulfide indicate that polycrystalline samples are more homogeneous, on a microscopic level, than the large single crystals used in previous work. Raman line broadening in a sample of naphthalene in which strain is induced intentionally by grinding and compression is also investigated.