  Polariton emission from optical cavities integrated with various luminophores
has been extensively studied recently due to the wide variety of possible
applications in photonics, particularly promising in terms of fabrication of
low-threshold sources of coherent emission. Tuneable microcavities allow
extensive investigation of the photophysical properties of matter placed inside
the cavity by deterministically changing the coupling strength and controllable
switching from weak to strong and ultra-strong coupling regimes. Here we
demonstrate room temperature strong coupling of exciton transitions in
CdSe/ZnS/CdS/ZnS colloidal quantum dots with the optical modes of a tuneable
low-mode-volume microcavity. Strong coupling is evidenced by a large Rabi
splitting of the photoluminescence spectra depending on the detuning of the
microcavity. A coupling strength of 154 meV has been achieved. High quantum
yields, excellent photostability, and scalability of fabrication of QDs paves
the way to practical applications of coupled systems based on colloidal QDs in
photonics, optoelectronics, and sensing.
