In this study, the “particle in a box” idea, which was broadly developed in semiconductor quantum dot research, was extended into mid-infrared (IR) cavity modes by applying lateral confinement in an optical cavity. The discrete cavity modes hybridized with molecular vibrational modes, resulting in a quartet of polariton states that can support multiple coherence states in the IR regime. We applied tailored pump pulse sequences to selectively prepare these coherences and verified the multi-coherence existence. The simulation based on Lindblad equation showed that because the quartet of polariton states resided in the same cavity, they were specifically robust toward decoherence caused by fluctuations in space. The multiple robust coherences paved the way for entangled states and coherent interactions between cavity polaritons, which would be critical for advancing polariton-based quantum information technology.

Vibrational polaritons have shown to modify chemical reactions, and thus, understanding its vibrational energy dynamics is a key to rationally design polariton chemistry. In this work, using tailored two-dimensional infrared pump probe spectroscopy and a modified transfer matrix model, we showed that the Raman-active Eg mode plays role in energy relaxation process of W(CO)6 polariton system. Precisely, after LP excitation, instead of relaxing to the 1st and 2nd excited state of T1u dark modes, a certain population of LP scatters through a phonon-assisted process to the Eg mode, which later decays into the population of T1u states. The involvement of the Eg mode, which was not considered in previous polariton studies, indicates the importance of considering non-IR active modes in polariton chemistry and dynamics. Furthermore, the current study indicate a viable pathway that polariton influence chemistry, by open up vibrational dynamic channels that are inaccessible under regular conditions.