Observation of Rabi splitting in a bulk GaN microcavity grown on silicon

We report the experimental observation of the strong-coupling regime in a nitride-based microcavity. The active layer in the optical cavity consists of a lambda/2 GaN layer sandwiched between a dielectric mirror and the silicon substrate, which acts as the bottom mirror. Reflectivity measurements have been performed under various angles of incidence at T=5 K, producing evidence of strong-coupling behavior between the exciton and the cavity mode. A Rabi splitting of 31 meV is obtained experimentally. Transfer-matrix simulations have allowed us to account for the exciton-photon interaction. From these calculations, the oscillator strengths of the A and B excitons are evaluated and these values are in good agreement with those previously determined in bulk GaN.