Strong coupling at room temperature in ultracompact flexible metallic microcavities

Strong coupling between metallic microcavity modes and inorganic quantum well (QW) excitons at room temperature is observed in an ultracompact flexible sample design less than 100 nm thick. Four GaAs QWs embedded in a 65 nm AlGaAs/GaAs cavity are sandwiched between gold mirrors. The strong electromagnetic confinement and metallic phase shifts provide substantial local field enhancement and angular-resolved reflectivity spectra clearly show the anti-crossing in the dispersion relation resolving a Rabi splitting of 21 meV at room temperature, in good agreement with calculations. Flex-tuning metal thin foil microcavities demonstrate new possibilities for tunable optoelectronics and the study of polaritonic micromechanical effects.