Control of Vibration-Cavity Polaritons in the Frequency and Time Domains*

We focus on light-matter interactions to alter the chemical behavior of molecular species. Strong coupling to molecular vibrations creates vibrational polaritons enabling modified energetics and, potentially, the ability to control chemical reactivity and energy relaxation. We will describe strong coupling between a Fabry-Pérot cavity and several molecular species (e.g., polymers and solvated species) and investigate the transition from the strong to weak coupling regimes. We map the influence of molecule/cavity mode overlap by systematically altering the position of a molecular slab throughout the first and second order cavity. In the time domain, pump-probe infrared spectroscopy is used to characterize the dynamics of vibration-cavity polaritons revealing quantum beats and excited-state absorption from polaritons and uncoupled reservoir modes. Polaritons relax ten times more quickly than uncoupled vibrations and exhibit a cavity tuning-dependent lifetime due to mixed cavity and molecular character of the polariton. Since energy relaxation depends on cavity-vibration coupling, it may provide opportunities to influence chemical reactivity.