Whispering-Gallery Quantum-Well Exciton Polaritons in an Indium Gallium Arsenide Microdisk Cavity

Despite appealing high-symmetry properties that enable high quality factor and strong confinement, whispering gallery modes of spherical and circular resonators have been absent from the field of quantum-well exciton polaritons. Here we observe whispering gallery exciton polaritons in a Gallium Arsenide microdisk cavity filled with Indium Gallium Arsenide quantum wells, the testbed materials of polaritonics. Strong coupling is evidenced in photoluminescence and resonant spectroscopy, accessed through concomitant confocal microscopy and near-field optical techniques. Excitonic and optical resonances are tuned by varying temperature and disk radius, revealing Rabi splittings between 5 and 10 meV. A dedicated analytical quantum model for such circular polaritons is developed, which reproduces the measured values. At high power, lasing is observed and accompanied by a blueshift of the emission that points to the regime of polariton lasing.