On-Chip Plasmonic Slit-Cavity Platform for Room-Temperature Strong Coupling with Deterministically Positioned Colloidal Quantum Dots.

Strong coupling between quantum emitters and optical cavities underpins many quantum photonic technologies, yet achieving this regime at room temperature in compact, deterministic on-chip platforms remains challenging due to the difficulty of fabricating cavities with ultrasmall mode volumes and precisely positioning quantum emitters. Here, we demonstrate a robust quantum plasmonic device in which colloidal quantum dots are strongly coupled to plasmonic slit cavities. Our dielectrophoresis-based positioning technique with real-time photoluminescence feedback enables parallel device fabrication and straightforward integration with additional optical elements, such as waveguides. Our measurements reveal clear photoluminescence-resolved Rabi splitting at room temperature in precharacterized cavities, with device-to-device variations scaling with the average number of coupled quantum dots. While electrical tuning via the quantum-confined Stark effect is enabled by integrated electrodes, its impact is largely overshadowed by room-temperature spectral diffusion. These results establish a scalable and electrically addressable plasmonic platform for room-temperature quantum technologies.