Tailoring the strong coupling regime in III-nitride based microcavities for room temperature polariton laser applications
We report on the properties of III-nitride based microcavities (MCs) operating in the strong coupling regime (SCR) up to room temperature. We first discuss why this class of materials is well suited to investigate the physics of cavity polaritons, which are admixed particles resulting from the coupling between cavity photons and excitons. In addition to the high quality of the different building blocks forming the MC, we point out the role of the active medium geometry, and in particular, the impact of the quantum well number and the distribution of the latter to maximize the vacuum Rabi splitting. Thanks to a well grounded SCR at high temperatures, we demonstrate polariton lasing in the 180-340 K range whose threshold is mainly governed by thermally activated detrapping mechanisms. Since the trap depth formed by the lower polariton branch is fixed by the exciton-cavity photon detuning (delta), it is shown that the polariton escape rate from the trap and hence the threshold power density strongly depend on this parameter. Experimental results are well accounted for when using a simplified thermodynamic model that reproduces the threshold behavior as a function of gin the temperature range investigated.