Influence of the excitonic broadening on the strong light-matter coupling in bulk zinc oxide microcavities

We present an experimental study of the influence of excitonic broadening on the strong-coupling regime in a bulk-ZnO microcavity. At room temperature, the strong coupling is highlighted using both angle-resolved reflectivity and photoluminescence measurements; a Rabi splitting value of 40 meV is determined. The polaritonic behavior is also evidenced at low temperature, even if a bulklike reflectivity signature is observed in the excitonic range. Using transfer-matrix calculations, this phenomenon is explained through the influence of the huge excitonic absorption whose contribution depends on the broadening value. Finally, we demonstrate that this effect should not prevent a lasing from the polaritons. (C) 2010 American Institute of Physics. [doi:10.1063/1.3476553]