Nanoimaging and control of molecular vibrations through electromagnetically induced scattering reaching the strong coupling regime

Optical resonators, such as plasmonic nanoparticles and optical microcavities, have garnered significant attention recently as a way to enhance and modify the light-matter interaction. The long lifetimes of IR active molecular vibrations combined with the strongly subwavelength optical mode volumes of nanophotonic resonators offer an opportunity to observe novel phenomena through coupled multilevel systems with engineered light matter interactions and modification of vibrational excitation.
We demonstrate the use of a nanotip and resonant optical nanowire to control excitation of molecular vibrations through near-field coupling. We measure induced polarization in the near-field using broadband synchrotron infrared nanospectroscopy (SINS). We quantify femtosecond coupling strengths up to 47 cm^-1, occuring faster than the intrinsic vibrational dephasing and approaching the strong coupling regime. By tuning optical excitation of both the nanotip and nanowire, we control interference between the resonators. Finally, we observe novel effects from electromagnetically induced scattering (EIS) of molecular vibrations. These results demonstrate a new regime of IR vibrational nano-spectroscopy with multiresonator behavior modifying vibrational coherence within few molecule sample volumes.