Picosecond Phonon-Polariton Pulse Transmission through an Interface

The coherent transmission of a short phonon-polariton pulse through a vacuum layer separating two identical noncentrosymmetric crystals (ammonium chloride) is investigated in real time and space by use of the nonlocal time-resolved coherent anti-Stokes Raman scattering technique. We show that this technique permits a local tracking of the phonon-polariton evolution as it interacts with boundaries, yielding selective information on the impact of an interface on the polariton wave-packet coherence.