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Register a new userNonlinear dynamics of polariton scattering in semiconductor microcavity: bistability vs stimulated scattering
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Authors
N. A. Gippius
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We demonstrate experimentally an unusual behavior of the parametric polariton scattering in semiconductor microcavity under a strong cw resonant excitation. The maximum of the scattered signal above the threshold of stimulated parametric scattering does not shift along the microcavity lower polariton branch with the change of pump detuning or angle of incidence but is stuck around the normal direction. We show theoretically that such a behavior can be modelled numerically by a system of Maxwell and nonlinear Schroedinger equations for cavity polaritons and explained via the competition between the bistability of a driven nonlinear MC polariton and the instabilities of parametric polariton-polariton scattering.
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Microcavity polaritons are composite half-light half-matter quasi-particles, which have recently been demonstrated to exhibit rich physical properties, such as non-equilibrium Bose-Einstein condensation, parametric scattering and superfluidity. At the same time, polaritons have some important advantages over photons for information processing applications, since their excitonic component leads to weaker diffraction and stronger inter-particle interactions, implying, respectively, tighter localization and lower powers for nonlinear functionality. Here we present the first experimental observations of bright polariton solitons in a strongly coupled semiconductor microcavity. The polariton solitons are shown to be non-diffracting high density wavepackets, that are strongly localised in real space with a corresponding broad spectrum in momentum space. Unlike solitons known in other matter-wave systems such as Bose condensed ultracold atomic gases, they are non-equilibrium and rely on a balance between losses and external pumping. Microcavity polariton solitons are excited on picosecond timescales, and thus have significant benefits for ultrafast switching and transfer of information over their light only counterparts, semiconductor cavity lasers (VCSELs), which have only nanosecond response time.
Polariton spin carries the combination of the exciton and the photon spin, which is manifested in the circularly polarized emission degree in a III-V quantum wells microcavity system. Relaxation process of such spin system is a complex subject since it involve upper or lower polariton branch, resonant or non resonant polariton excitation process and if the particles are in strong or weak coupling regime. We present here experimental polariton spin Faraday rotation time measurement in GaAs single quantum well microcavity, using time resolved polariton photoluminescence by resonant excitation process in a pump-probe system.
We demonstrate for the first time the strong temporal hysteresis effects in the kinetics of the pumped and scattered polariton populations in a planar semiconductor microcavity under a nano-second-long pulsed resonant (by frequency and angle) excitation above the lower polariton branch. The hysteresis effects are explained in the model of multi-mode scattering when the bistability of the nonlinear pumped polariton is accompanied by the explosive growth of the scattered polaritons population. Subsequent self-organization process in the nonlinear polariton system results in a new -- dynamically self-organized -- type of optical parametric oscillator.
We demonstrate a novel kind of polariton four wave mixing oscillation. Two pump polaritons scatter towards final states that emit two beams of equal intensity, separated both spatially and in polarization with respect to the pumps. The measurement of the intensity fluctuations of the emitted light demonstrates that the final states are strongly correlated.
A method of determining the temperature of the nonradiative reservoir in a microcavity exciton-polariton system is developed. A general relation for the homogeneous polariton linewidth is theoretically derived and experimentally used in the method. In experiments with a GaAs microcavity under nonresonant pulsed excitation, the reservoir temperature dynamics is extracted from the polariton linewidth. Within the first nanosecond the reservoir temperature greatly exceeds the lattice temperature and determines the dynamics of the major processes in the system. It is shown that, for nonresonant pulsed excitation of GaAs microcavities, the polariton Bose-Einstein condensation is typically governed by polariton-phonon scattering, while interparticle scattering leads to condensate depopulation.
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