Résumé
We experimentally demonstrate polariton laser in a GaN ridge waveguide. The strong-coupling regime is assessed through a comparison of the measured and modeled cavity free spectral range (FSR). The findings reveal that the laser exhibits a transition from monomode to multimode operation as the temperature is increased from 70K to 150K. The transition to multimode lasing is characterized by a flattening of the FSR just above the threshold, which constitutes the signature of mode synchronization induced by polaritonic nonlinearities.