Publication date: 17th July 2025
We investigate single CsPbBr3 quantum dots (QDs) as quantum light sources operating at cryogenic temperatures. The 25 nm large QDs are placed into a tunable, open Fabry-Pérot microcavity with a wavelength-scale Gaussian deformation to enhance their radiative decay rate and brightness via the Purcell effect. The acceleration of the emission is quantified by the Purcell factor, FP, which is proportional to the ratio between the quality factor, Q, and the effective modal volume, V, of the cavity, and is maximized when the QD is spectrally and spatially in resonance with a cavity mode. This cylindrically symmetric cavity configuration supports Laguerre-Gaussian (LG) modes that are associated with non-zero orbital angular momentum (OAM), which is of interest for quantum communication and sensing applications. Coupling the QD emission to these modes enables the direct generation of single photons in well-defined LG states selected by tuning of the cavity length.
We realize Purcell-enhanced emission with FP = 4.2 at 6 K, where however the measured cavity-accelerated decay is limited by the instrumental time resolution. At 50 K, where the radiative decay time of perovskite QDs is longer, we find up to FP = 18.1, closer to the theoretical maximum of FP = 38 for our cavity. The lifetime reduction is accompanied by enhanced brightness and purity due to funnelling of the emitted photons into one specific mode and suppression of parasitic emission like biexcitons, as evidenced by improved photon anti-bunching.
Furthermore, by in-situ tuning of the cavity, we can bring different LG modes into resonance with the QD emission. We show that the emitted single-photon streams have LG spatial profiles of different radial and azimuthal orders, selected by tuning of the cavity resonance.
Our work demonstrates effective generation of single photons from colloidal perovskite QDs in controllable LG modes, which are promising for quantum photonic applications that use OAM states.
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