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Register a new userPolariton spin Faraday rotation dynamics in a GaAs microcavity
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Added by
Thonimar Vieira de Alencar Souza
Publication date
2011
fields
Physics
and research's language is
English
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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.
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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.
Entanglement generation in microcavity exciton-polaritons is an interesting application of the peculiar properties of these half-light/half-matter quasiparticles. In this paper we theoretically investigate their luminescence dynamics and entanglement formation in single, double, and triple cavities. We derive general expressions and selection rules for polariton-polariton scattering. We evaluate a number of possible parametric scattering schemes in terms of entanglement, and identify the ones that are experimentally most promising.
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.
Biexciton emission properties were studied in a single GaAs quantum well semiconductor planar microcavity by photoluminescence measurements at low temperatures. At high pump intensity a bipolariton emission appears close to the lower polariton mode. This new mode appears when we detune the cavity resonance out of the lower polariton branch, showing a laser like behavior. Very small lines widths were measured, lying below 110 μeV and 150 μeV for polariton and bipolariton emission respectively. The input/output power (I/O) measurements show that the bipolariton emission has a weaker coupling efficiency compared to previous results for polariton emission. Simultaneous photoluminescence and near field measurements show that the polariton and bipolariton emission are spectrally and spatially separated.
Periodic structures resonantly coupled to excitonic media allow the existence of extra intragap modes (Braggoritons), due to the coupling between Bragg photon modes and 3D bulk excitons. This induces unique and unexplored dispersive features, which can be tailored by properly designing the photonic bandgap around the exciton resonance. We report that one-dimensional Braggoritons realized with semiconductor gratings have the ability to mimic the dispersion of quantum-well microcavity polaritons. This will allow the observation of new nonlinear phenomena, such as slow-light-enhanced nonlinear propagation and an efficient parametric scattering at two magic frequencies.
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