Coupling Among Dark Excitons, Bright Excitons, and Photons in Semiconducting Carbon Nanotube Microcavity Polaritons

Semiconducting single-walled carbon nanotubes (SWCNTs) are an exquisite candidate for realizing stable room-temperature exciton-polaritons. They possess a combination of bright and dark excitonic states, with the latter sometimes “brightened” by vibrational transitions through external oscillation energies (e.g., a phonon). Yet, manipulating such dark excitonic states is tedious, given their weak coupling strengths. We show here that strong light-matter interaction allows for hybridization of bright and dark excitonic states mediated by a common cavity photon and exciton-phonon coupling. This coupling creates new eigenstates at tunable wavelengths that were formally non-emissive, in addition to the conventional polaritonic states that arise from typical excitonic transitions. This unique interaction is demonstrated in an optical cavity containing high density (>40 wt%) (6,5) SWCNTs. The high quality-factor of the cavity fabricated by a custom lamination approach have enabled us to accomplish high coupling strengths of >90meV for the dark exciton-phonon-photon coupled states. The large SWCNT density and the lamination technique also result in ultra-strong coupling between bright exciton and photon states, with a Rabi splitting of ∼450meV and narrow band emission (FWHM of 30 meV).