Purcell Enhanced Emission and Saturable Absorption of Cavity-Coupled CsPbBr₃ Quantum Dots

Halide perovskite semiconductors have emerged as promising materials for the development of solution-processed, scalable, and high-performance optoelectronic devices such as light-emitting diodes (LEDs) as well as coherent single photon emitters. Their integration into nanophotonic cavities for radiative enhancement and strong nonlinearity is underexplored. In this work, we demonstrate cavity-enhanced emission and saturable absorption using colloidal CsPbBr3 perovskite quantum dots coupled to a high-Q cavity mode of a circular Bragg grating structure designed to facilitate the integration of solution-processed materials. We achieve an order of magnitude increase in brightness and an 8-fold increase in the spontaneous emission rate for the cavity-coupled emitters. This result indicates the possibility of achieving transform-limited photon coherence for the halide perovskites at cryogenic temperatures. We also observe saturable absorption of the emitters through the intensity-dependent cavity quality factor. These results pave the way toward achieving improved photon indistinguishability and strong optical nonlinearities for cavity-coupled perovskite systems.