Observation of exciton-polariton ladder in semiconductor microcavity

Summary form only given. Control of spontaneous emission in a semiconductor microcavity has attracted a lot of interest and investigation, as a result of its fundamental cavity QED aspects and its application to low threshold or even thresholdless lasers. In the strong coupling regime, the coupled exciton-polariton mode splitting has been observed, and the cavity-polariton dispersion curve has shown anti-crossing behavior. However, in those cases only one quantum well exciton mode interacts with one cavity photon mode. We have investigated the case where many exciton modes couple with a single cavity photon mode. Theoretical calculation shows that when the separation between adjacent exciton modes is much larger than the Rabi splitting of one exciton mode with the photon mode, the photon mode will couple with only one exciton mode at a time, and the dispersion curves show many anti-crossings. However, if the exciton mode separation is much smaller than the exciton-polariton coupling, the photon mode will couple with several exciton modes simultaneously. The Rabi splitting will be clamped by mode separation, and the anti-crossing of the dispersion curve is diminished.