Self-oscillations in GaAs microcavity: Polariton and photon laser superposition

•The presence of self-oscillations in the emission intensity.•Self-oscillations presenting different waveforms as periods with time scale of microseconds.•First experimental evidence of the self-phase modulation effect in high pump intensities.•Self-phase modulation presenting a chaotic behaviour.•Coexistence of polariton laser and photon laser simultaneously.

In this paper we identify experimentally an unstable polariton laser emission through cavity spontaneous self-oscillations when excited resonantly in continuous mode. The experimental results indicate the coexistence of a laser state (in a non-condensed state) and a condensate state of polaritons, in which the former would be under self-phase modulation effect. These oscillations present different waveforms, indicating a chaotic behaviour in the phase of the polariton states emission. This is a novel experimental indicative of the polariton condensation in semiconductor microcavities, in which a quantitative analysis results in ~72% of polaritons composing this state.