摘要： All-inorganic lead halide perovskites are ideal platforms to investigate the fundamental physics of the light-matter interactions, due to their strong oscillator strength at room temperature and various microstructures. In this paper, we investigated strong exciton-photon coupling and coherent photonic lasing in a same high-quality self-assembled CsPbBr3 perovskite microcuboid grown by a chemical vapor deposition method. The vacuum Rabi splitting of polariton up to 309 meV, and the exciton-like and photon-like components in low polariton states at different cavity-exciton detuning, were revealed by angle-resolved photoluminescence spectra at room temperature. Moreover, we realized a coherent photonic lasing with a high quality-factor (4153) and narrow linewidth (0.13 nm) in the microcuboid above threshold (16 μJ/cm2), originated from population inversion. Significantly, the interference pattern of the coherent lasing through the Young's double-slit interference method based on far-field Fourier optical system, directly indicate the parity (odd) of the lasing mode and the asymmetric electric-field distribution in the CsPbBr3 microstructure. Our work demonstrates for the first time a transition from the strong coupling regime (vertical Fabry–Pérot oscillation) to weak coupling regime (lateral Fabry–Pérot oscillation) in such self-assembled microcuboid under the competition between gain and internal loss. Based on this mechanism, a considerable promise is expected to enrich the functions of micro-nano structure photoelectric devices by precisely controlling the quality-factor and gain of such microstructure.