  We report on the quantum confinement of zero-dimensional polaritons in
perovskite-based microcavity at room temperature. Photoluminescence of discrete
polaritonic states are observed for polariton localized in symmetric
sphere-like defects which are spontaneously nucleated on the top dielectric
Bragg mirror. The linewidth of these confined states are found much sharper
(almost one order of magnitude) than that of photonic modes in the perovskite
planar microcavity. Our results show the possibility to study organic-inorganic
cavity polariton in confined microstructure and suggest a fabrication method to
realize integrated polaritonic devices operating at room temperature.
