Lead halide perovskite quantum dots have recently emerged as promising nano-emitters due to their excellent optical properties, including high brightness, tunable optical bandgap, reduced blinking, and easy and low-cost fabrication [1]. These properties make them potential candidates for realising a new generation of optoelectronic devices such as light-emitting diodes (LEDs), lasers, or photodetectors. At the individual quantum dot level, single photon emission at room temperature [2,3], long coherence times and photon indistinguishability with 50% visibility at cryogenic temperatures [4,5] have also been reported. These properties suggest that perovskite quantum dots could play a key role in the realisation of efficient single-photon sources based on solution-processed nanoemitters for applications in quantum optics and quantum communication. In this context, one of the main challenges is to couple individual perovskite quantum dots to optimised photonic structures in order to control and enhance the spontaneous emission properties of the nano-emitters using cavity quantum electrodynamics (cQED) effects.

In this talk I will present our recent results on cQED experiments on single perovskite quantum dots coupled to an optical microcavity. We have designed and implemented a reconfigurable open fibre-based Fabry-Pérot microcavity, specifically suited for CsPbBr₃ perovskite quantum dots. It is based on a highly versatile setup that has previously been successfully optimised for single carbon nanotubes [6]. Unlike conventional monolithic microcavities, which are designed to ensure spatial and spectral matching to a specific nano-emitter and cannot be subsequently modified, this fibre microcavity is perfectly suited to solution-processed nano-emitters. It consists of a planar mirror on which the quantum dots are deposited and a movable concave fibre mirror. This geometry allows us both to ensure spatial and spectral matching for different perovskite quantum dots and to study the same nano-emitter in free space and in cavity configurations. I will show that previously characterised single CsPbBr₃ quantum dots [7,8] have been successfully coupled to this microcavity. By comparing their photoluminescence lifetime in free space with that in the cavity configuration, a twofold acceleration of the emission lifetime due to the Purcell effect was consistently observed, corresponding to Purcell factors of up to 4.5. Furthermore, the reversible coupling of individual CsPbBr₃ quantum dots to the cavity provides a highly interesting tool to precisely analyse the modification of the spectral features induced by the cavity coupling and to extract fundamental properties such as the vacuum Rabi coupling, which is of the order of 30 µeV in our system. These results pave the way for the realisation of a narrow-band efficient single-photon source at the cavity resonance frequency in the weak coupling regime using perovskite quantum dots.