Polariton condensation phase diagram in wide bandgap planar microcavities: GaN versus ZnO

TL;DR

This study compares the polariton condensation phase diagrams in GaN and ZnO microcavities, revealing how phonon interactions and material properties influence lasing thresholds across temperatures.

Contribution

It provides a direct experimental and simulation-based comparison of polariton condensation in GaN and ZnO microcavities under identical conditions, highlighting relaxation mechanisms.

Findings

Lower polariton lasing threshold in ZnO at low temperature due to larger Rabi splitting

LO phonons significantly affect polariton relaxation and thresholds

Room temperature thresholds are similar in both microcavities

Abstract

GaN and ZnO microcavities have been grown on patterned silicon substrate. Thanks to a common platform these microcavities share similar photonic properties with large quality factors and low photonic disorder which gives the possibility to determine the optimal spot diameter and to realize a complete comparative phase diagram study. Both systems have been investigated under the same experimental condition. Experimental results are well reproduced by simulation using Boltzmann equations. Lower polariton lasing threshold has been measured at low temperature in the ZnO microcavity as expected due to a larger Rabi splitting. However the threshold is strongly impacted by LO phonons through phonon-assisted polariton relaxation. We observe and discuss this effect as a function of temperature and detuning. Finally the polariton lasing threshold at room temperature is quite similar in both microcavities. This study highlights polariton relaxation mechanism and their importance for threshold optimization.