Integration of quantum dots at the tips of single plasmonic bipyramid nanoantennas for strong coupling at room temperature

Achieving strong coupling between excitons of colloidal semiconductor quantum dots (QDs) and localized surface plasmon polaritons (LSPs) is critical for advanced room-temperature quantum emitter and sensing applications. A key challenge is to have precise control of the emitters position with respect to an individual plasmonic nanostructure. Here, we present room temperature strong coupling between QDs and a single gold nano-bipyramid (BPs). The selection of the bipyramid plasmonic nanocavity offers access to a single hotspot with a very small mode volume. The localization of QDs at a single hotspot is achieved via plasmon-triggered two-photon polymerization. This technique exploits the enhanced electric field at the BP tip to selectively polymerize a photosensitive QD-containing formulation. Room-temperature scattering spectra of a 3-QD-BP system reveal Rabi splitting of 349.3 meV and a coupling strength of 175.68 meV. The with distinct anti-crossing behavior is confirmed by simulations. This approach simplifies QD integration for strong coupling systems compared to previous methods. These results indicate a scalable platform for solid-state quantum technologies with colloidal QDs, enabling explora-tion of exciton-plasmon interactions and further advance-ment of applications in quantum optics and quantum sensing under ambient conditions.