  We present experimental observation of the strong light-matter coupling
regime in ZnO bulk microcavities grown on silicon. Angle resolved reflectivity
measurements, corroborated by transfer-matrix simulations, show that Rabi
splittings in the order of 70 meV are achieved even for low finesse cavities.
The impact of the large excitonic absorption, which enables a ZnO bulk-like
behavior to be observed even in the strong coupling regime, is illustrated both
experimentally and theoretically by considering cavities with increasing
thickness.
