Résumé
Semiconductor-based microcavities appear as a prolific system for studying light-matter interaction between a spatially-confined photonic mode and an excitonic resonance. The quasiparticles arising from this coupling (microcavity-polaritons) have enabled in the last years the observation of new lasing regimes as well as polariton Bose-Einstein condensates, vortices and lately solitons. In this panorama ZnO appears as an alternative material to more mature ones, such as GaAs or CdTe, with larger oscillator strengths and enhanced exciton stability. These two properties render ZnO very interesting for studies and applications where large particle densities and/or high temperatures are required. However, the fabrication of ZnO-based microcavities is still challenging and it often requires the use of either nitrides or dielectric materials for the DBRs. Indeed, polariton lasing was demonstrated for the first time in a ZnO-based microcavity only in 2011 [1, 2]. In this work we report on the optical study of a fully-hybrid ZnO-based microcavity in which we combine a high quality active region made up of bulk ZnO and a high cavity quality factor, thanks to the use of two dielectric DBRs. Indeed, the Q-factor of the cavity measured by micro-reflectivity exceeds systematically 1000. Furthermore, as the ZnO active region has a wedge shape a large range of detuning between the cavity and the excitonic mode is accessible. Polariton lasing, as characterized by a strong (typically a factor 5) linewidth reduction, a small blueshift compared to the Rabi splitting (typically 30 times smaller), and an increased intensity emission (four orders of magnitude increase) will be reported. The study of the lasing regime as a function of temperature and detuning will be presented and the differences with respect to other materials, arising due to ZnO peculiarities, will be emphasized. [1] T. Guillet et al., Appl. Phys. Lett. 99 (2011) 161104. [2] L. Orosz et al., Phys. Rev. B.(2012) accepted for publication.