Infoscience

Thesis

Noise-Induced Phenomena in Collective Spinor Polariton Excitations

Polaritons are quasiparticles resulting from the strong coupling between photons and excitons embedded in a semiconductor microcavity. The exciton component of polaritons provides strong nonlinear interactions, while their photonic counterpart facilitates long range coherence. Moreover, polaritons carry a pseudospin that can be accessed through the polarization state of the emitted light, and brings up spinor related nonlinear effects. This study aims at in-depth investigation of the noise related phenomena in polariton system. First, a series of experiments of polariton bistability and multistability are performed to deepen our knowledge about the effect of the biexciton creation and polariton-polariton interaction on multistable regimes in exciton polaritons. Then, using an external Gaussian noise, the polariton transition rate between two stable states of a polariton bistability is characterized. It is shown that the external noise specifications, intensity and correlation time, can efficiently modify the polariton Kramers time and residence time. We also discuss the performance of the bistable behaviour in steady state regime in terms of experimental acquisition time compared to the noise-assisted residence time. In the next part, taking advantage of polariton bistability and spin-trigger regime, we have evidenced two different types of stochastic resonance. Intensity stochastic resonance and spinor stochastic resonance. We have shown that the synergic interplay between intensity fluctuations and external modulated signal, imprinted on the DC component of the driving field, can enhance the coherent processing of an input signal buried in noise. Moreover, we evidence that, due to the exceptional spin properties of polaritons, a noisy modulated polarized input signal can drive the switching of a fully polarized polariton population. This effect unveils an original field of stochastic resonance which we called as spinor stochastic resonance. All experimental results are well reproduced by a model based on Gross-Pitaevskii equation. At the end, the influence of nonlinear interactions on polariton intensity fluctuations and probability distribution have been investigated.

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