Regimes of enhanced optical bistability: The effect of external-signal noise

Sergei N Bagaev, V. A. Nikulin, Е. А. Титов

Sergei N Bagayev, A. A. Kurbatov, P.V. Pokasov +1 more

Claudia Yu. Zenkova

The impact of a weak external magnetic field upon the conditions of optical bistability (OB) realization in the exciton absorption region of layer semiconductors has been investigated. With the 2H-polytype PbI2 used as an example, the possibility of obtaining the OB realization region by changing the external magnetic field intensity has been shown. This effect can be used as a basic guideline in measuring the level of laser radiation signals, and can provide means for metrological maintenance of systems working in different active regime.

Axel Schenzle

Hadis Abbaspour

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.

Haibin Wu, Surendra Singh, Min Xiao

Effects of multiplicative noise on optical bistability in a three-level atomic medium in a ring cavity are investigated experimentally and theoretically. Steady-state intensity distributions as well as switching and dwell times have been measured as functions of noise strength. System response to an external periodic signal is also explored. It is found that the probability for the system to stay in the upper state increases with increasing noise strength. When a small periodic signal is added to the input field, the probability for the upper state has a maximum as a function of multiplicative noise strength. A simple theoretical model based on nonlinear atomic susceptibility is presented to interpret the experimental observations.