Active tuning of near-infrared interaction of single-walled carbon nanotubes with quasibound states in the continuum in all-dielectric metasurfaces

Single-walled carbon nanotubes (SWCNTs), with their high oscillator strength and large exciton binding energies, are becoming highly promising materials for the study of exciton-polaritons in the near infrared (NIR) at room temperature. However, current SWCNT-based strong coupling systems generally involve either lossy plasmonic nanostructures or bulk cavity-type resonators with poor compactability and tunability. Here, an ultracompact and low-loss all-dielectric metasurface combined with a phase change material (PCM) is proposed to enable active tuning of SWCNT-based exciton-polaritons in the NIR region. We demonstrate control of exciting quasibound states in the continuum (QBICs) by changing temperatures in the metasurface, which enables an active and flexible tuning exciton-QBIC interactions. We reveal that the dominant excitations of the magnetic dipole and high-order electric quadrupole at QBIC resonance play an important role in field enhancement, thus greatly facilitating the exciton-QBIC interaction. A quantum model fully describes the microscopic coupling dynamics, demonstrating a temperature-dependent sub- and superradiance of the polariton states. We also demonstrate a linear dependence of exciton-QBIC coupling strength on the SWCNT concentrations, which may provide an efficient approach for observing ultrastrong coupling phenomena. The PCM-assisted active tuning of exciton polaritons is expected to enable ultrafast and highly compact polariton devices at telecommunication wavelengths.