Spin polarization dynamics of an exciton-polariton condensate in a ring microcavity with artificial gravity (original) (raw)
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Energy relaxation of exciton-polariton condensates in quasi-one-dimensional microcavities
Physical Review B, 2013
We present a time-resolved study of energy relaxation and trapping dynamics of polariton condensates in a semiconductor microcavity ridge. The combination of two non-resonant, pulsed laser sources in a GaAs ridge-shaped microcavity gives rise to profuse quantum phenomena where the repulsive potentials created by the lasers allow the modulation and control of the polariton flow. We analyze in detail the dependence of the dynamics on the power of both lasers and determine the optimum conditions for realizing an all-optical polariton condensate transistor switch. The experimental results are interpreted in the light of simulations based on a generalized Gross-Pitaevskii equation, including incoherent pumping, decay and energy relaxation within the condensate.
Applied Physics Letters, 2014
We comparably investigate the diamagnetic shift of an uncoupled quantum well exciton with a microcavity exciton polariton condensate on the same device. The sample is composed of multiple GaAs quantum wells in an AlAs microcavity, surrounded by a Bragg reflector and a sub-wavelength high contrast grating reflector. Our study introduces an independent and easily applicable technique, namely the condensate diamagnetic shift which directly probes matter contributions in polariton condensates and hence discriminates it from a conventional photon laser.
Phase diagram for condensation of microcavity polaritons: From theory to practice
Physical Review B, 2008
The first realization of a polariton condensate was recently achieved in a CdTe microcavity [Kasprzak et al., Nature 443, 409 (2006)]. We compare the experimental phase boundaries, for various detunings and cryostat temperatures, with those found theoretically from a model which accounts for features of microcavity polaritons such as reduced dimensionality, internal composite structure, disorder in the quantum wells, polariton-polariton interactions, and finite lifetime.
Dynamics of Interactions of Confined Microcavity Polaritons
2010
de l'orientation des spins des polaritons. Sous excitation polarisée linéairement, la bistabilité est fortement réduite, voire supprimée. Nous montrons que cela est dûà un appariement des polaritons de spin opposés pour former des biexcitons. Nous démontrons le contrôle des différents régimes d'instabilité optiqueà travers la polarisation de l'excitation. Nous regardons ensuite le cas des polaritons confinés. En travaillant avec un uniqueétat confiné, nous obtenons un contrôle optique complet des interactions de spin entre polaritons. Nous démontrons pour la première fois la multistabilité d'un ensemble cohérent de spins dans l'état solide. Ce résultat est uneétape importante dans le cadre de la recherche sur la manipulation de spins pour le développement de dispositifs optoélectroniques. Finalement, nous montrons l'impact que pourrait avoir le spin des polaritons sur le couplage en polaritons de dimensionnalités différentes ainsi que sur le contrôle des régimes de propagation des fluides de polaritons. Nos expériences sont appuyées par des modèles théoriques. Nous proposons, en perspective, de nouvelles expériences sur la dynamique des polaritons et sur la manipulation cohérente de spins dans les microcavités.
We investigate the optical orientation, polarization pinning, and depolarisation of optically confined semiconductor exciton-polariton condensates performing a complete Stokes mapping of the condensate polarization and rotation of the polarization vector of a non-resonant optical pump both along the equator and the meridian of the Poincare sphere. We utilise a ring-shaped non-resonant optical excitation to generate an exciton-induced potential that spatially confines polariton condensates into a single mode. We observe that optical orientation of the condensate spinor parallel to the circular polarization of a non-resonant pump persists even for a small component of pump ellipticity, \$S\_3{\textbackslash}approx 0.03\$. By varying the ring diameter we realise a transition from the condensate polarization being pinned along the coordinate-dependent cavity-strain axes, to a regime of zero degree of condensate polarization under linearly polarized pump. Analysis through the driven-dissipative stochastic Gross-Pitaevskii equation reveals that depolarisation stems from a competition between a sample induced in-plane polarization splitting and the condensate-reservoir overlap. An increase in the role of the latter results in weakening of the condensate fixed-point phase space attractors, and enhanced presence of limit-cycle trajectories, effectively reducing the degree of time-integrated polarization.
Polariton Spinor Interactions in a GaAs-based microcavity
We report on spinor polariton interactions in GaAs based microcavity. This investigation is carried out by means of heterodyne polarized pump-probe spectroscopy. The results reveal the magnitude and the sign of interaction strength between polaritons with parallel and anti-parallel spins. We clearly show the dependence of the attractive and repulsive interaction constants with the cavity detuning. We evidence the strong influence of the biexciton resonance on the attractive interaction strength. Our modelization based on Gross-Pitaevskii equation reproduces the experimental observations. PACS numbers: 78.67. De, 71.36.+c Microcavity exciton polaritons are quasiparticles resulting from the strong coupling between excitons and photons . Polaritons exhibit mutual interactions coming from their excitonic content and light effective mass inherited from the photon. Moreover, the collected photons emitted from the cavity allow to read out the polaritons properties. As a matter of fact, a polariton fluid is an ideal tool for investigating quantum phenomena in solid-state systems. Polariton interactions in semiconductor microcavities play a crucial role in a wide variety of topics ranging from nonlinear optical effects, polariton superfluidity to Bose Einstein condensation. Their quantum coherence properties have been extensively investigated since the observation of polariton parametric processes [2-6]. First signs indicating spontaneous quantum degeneracy of polaritons appeared with the observation of stimulated emission under non-resonant excitation . In 2006, polariton Bose-Einstein condensation was demonstrated for the first time . Since then, many experiments have been performed to assess the superfluidity of polaritons, as well as the observation of full [10] and half quantized vortices, the demonstration of polariton flowing without scattering , and of solitons . The observation of the Bogoliubov excitations has been performed after initial indications of the linearization of the polariton dispersion .
Physical Review B, 2015
We realize the evaporative cooling of a polariton gas and observe the formation of polariton condensate in a potential trap based on a ZnO microwire at room temperature. Due to the three-dimensional confinement, the system is characterized by a well-defined discrete spectrum of polariton states which allows accurate measurements of the polariton population distribution. With increasing pumping power, the polariton gas system is cooled down very efficiently and relaxes closely to the thermal distribution via the polariton evaporative cooling. At an optimized excitation condition, the effective temperature of the polariton gas falls down to 22 K with the condensate fraction reaching nearly 50% in room temperature experiments.
Physical Review B, 2006
It is shown theoretically that Bose condensation of spin-degenerated exciton-polaritons results in spontaneous buildup of the linear polarization in emission spectra of semiconductor microcavities. The linear polarization degree is a good order parameter for the polariton Bose condensation. If spindegeneracy is lifted, an elliptically polarized light is emitted by the polariton condensate. The main axis of the ellipse rotates in time due to self-induced Larmor precession of the polariton condensate pseudospin. The polarization decay time is governed by the dephasing induced by the polaritonpolariton interaction and strongly depends on the statistics of the condensed state. Bose-condensation of exciton-polaritons (polaritons) in microcavities [1] is now in the focus of experimental and theoretical research. Possessing an extremely light effective mass (of the order of 4 10 − m 0 ), polaritons may condense even at room temperature provided that their lifetime is sufficiently long with respect to the characteristic thermalization time [2]. In realistic microcavities, polaritons may have a strongly non-equilibrium distribution in reciprocal space and their condensation is dramatically dependent on their relaxation dynamics. A clear experimental criterion for the condensation has been a subject for debate during recent years [3-4]. Stimulated scattering of polaritons to their ground state,