Coherent coupling between a molecular vibration and Fabry-Perot optical cavity to give hybridized states in the strong coupling limit (Presentation Recording)

Abstract

Coherent coupling between an optical-transition and confined optical mode, when sufficiently strong, gives rise to new modes separated by the vacuum Rabi splitting. Such systems have been investigated for electronic-state transitions, however, only very recently have vibrational transitions been considered. Here, we bring strong polaritonic-coupling in cavities from the visible into the infrared where a new range of static and dynamic vibrational processes await investigation. First, we experimentally and numerically describe coupling between a Fabry-Perot cavity and carbonyl stretch (~1730 cm 1) in poly-methylmethacrylate. As is requisite for “strong coupling”, the measured vacuum Rabi splitting of 132 cm 1 is much larger than the full width of the cavity (34 cm-1) and the inhomogeneously broadened carbonyl-stretch (24 cm-1). Agreement with classical theories providea evidence that the mixed-states are relatively immune to inhomogeneous broadening. Next, we investigate strong and weak coupling regimes through examination of cavities loaded with varying concentrations of urethane. Rabi splittings increases from 0 to ~104 cm-1 with concentrations from 0-20 vol% and are in excellent agreement to an analytical description using no fitting parameters. Ultra-fast pump-probe measurements reveal transient absorption signals over a frequency range well-separated from the vibrational band as well as modifications of energy relaxation times. Finally, we demonstrate coupling to liquids using the C-O stretching band (~1985 cm-1) of Mo(CO)6 in an aqueous solution. Opening the field of polaritonic coupling to vibrational species promises to be a rich arena amenable to a wide variety of infrared-active bonds that can be studied statically and dynamically.