Plasmonic Crystals for Strong Light–Matter Coupling in Carbon Nanotubes

[Image: see text] Their high oscillator strength and large exciton binding energies make single-walled carbon nanotubes (SWCNTs) highly promising materials for the investigation of strong light–matter interactions in the near infrared and at room temperature. To explore their full potential, high-quality cavities—possibly with nanoscale field localization—are required. Here, we demonstrate the room temperature formation of plasmon–exciton polaritons in monochiral (6,5) SWCNTs coupled to the subdiffraction nanocavities of a plasmonic crystal created by a periodic gold nanodisk array. The interaction strength is easily tuned by the number of SWCNTs that collectively couple to the plasmonic crystal. Angle- and polarization resolved reflectivity and photoluminescence measurements combined with the coupled-oscillator model confirm strong coupling (coupling strength ∼120 meV). The combination of plasmon–exciton polaritons with the exceptional charge transport properties of SWCNTs should enable practical polariton devices at room temperature and at telecommunication wavelengths.