Controling quantum pathways in the vibrational polaritons system

Molecular vibrational polaritons are hybrid quasi-particles between molecular vibrations and photons, through strong coherent light-matter coupling. It has attracted many attentions, because of its potential to alter photonic properties and also change the course of chemical reactions. Molecular vibrational polaritons have been studied by 2D infrared (2D IR) spectroscopy, which has advanced our understanding of the roles of dark states, hot excited state energy relaxation, and manipulation of nonlinear interactions in cavities. However, the coherent nature of polaritons imposes many quantum pathways contributing to the 2D IR signal, which complicates its interpretation and precision manipulation of quantum states. Using mid-IR pulse shaper, we report a way to selectively excite quantum pathways, to directly measure polariton nonlinear responses involving either coherence or population states. Because vibrational polariton forms a two-level system, it can serve a toy model to study the importance of coherence in energy transportation in energy materials. Thus, this work lays the foundation to prepare arbitrary quantum states in polaritons, for further exploration of the phenomena of nonlinear photonics, chemistry and quantum phenomena.