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Irákleion, Greece

Christmann G.,University of Cambridge | Tosi G.,University of Cambridge | Tosi G.,Autonomous University of Madrid | Tosi G.,University of New South Wales | And 9 more authors.
New Journal of Physics | Year: 2014

When pumped nonresonantly, semiconductor microcavity polaritons form Bose-Einstein condensates that can be manipulated optically. Using tightly-focused excitation spots, radially expanding condensates can be formed in close proximity. Using high time resolution streak camera measurements we study the time dependent properties of these macroscopic coherent states. By coupling this method with interferometry we observe directly the phase locking of two independent condensates in time, showing the effect of polariton-polariton interactions. We also directly observe fast spontaneous soliton-like oscillations of the polariton cloud trapped between the pump spots, which can be either dark or bright solitons. This transition from dark to bright is a consequence of the change of sign of the nonlinearity which we propose is due to the shape of the polariton dispersion leading to either positive or negative polariton effective mass. © 2014 IOP Publishing Ltd and Deutsche Physikalische Gesellschaft. Source


Christmann G.,University of Cambridge | Tosi G.,University of Cambridge | Tosi G.,Autonomous University of Madrid | Berloff N.G.,University of Cambridge | And 6 more authors.
Physical Review B - Condensed Matter and Materials Physics | Year: 2012

Optically pumping high-quality semiconductor microcavities allows the spontaneous formation of polariton condensates, which can propagate over distances of many microns. Tightly focused pump spots here are found to produce expanding incoherent bottleneck polaritons, which coherently amplify the ballistic polaritons and lead to the formation of unusual ring condensates in space. This quantum liquid is found to form a remarkable sunflowerlike spatial ripple pattern, which arises from self-interference with Rayleigh-scattered coherent polariton waves in the Cerenkov regime. © 2012 American Physical Society. Source


Anton C.,Autonomous University of Madrid | Liew T.C.H.,Nanyang Technological University | Tosi G.,Autonomous University of Madrid | Martin M.D.,Autonomous University of Madrid | And 6 more authors.
Applied Physics Letters | Year: 2012

We present a time-resolved study of the logical operation of a polariton condensate transistor switch. Creating a polariton condensate (source) in a GaAs ridge-shaped microcavity with a non-resonant pulsed laser beam, the polariton propagation towards a collector, at the ridge edge, is controlled by a second weak pulse (gate), located between the source and the collector. The experimental results are interpreted in the light of simulations based on the generalized Gross-Pitaevskii equation, including incoherent pumping, decay, and energy relaxation within the condensate. © 2012 American Institute of Physics. Source


Anton C.,Autonomous University of Madrid | Liew T.C.H.,Nanyang Technological University | Cuadra J.,Autonomous University of Madrid | Martin M.D.,Autonomous University of Madrid | And 7 more authors.
Physical Review B - Condensed Matter and Materials Physics | Year: 2013

We study the dynamics of polariton condensate wave trains that propagate along a quasi-one-dimensional waveguide. Through the application of tuneable potential barriers the propagation can be reflected and multiple reflections used to confine and store a propagating state. Energy-relaxation processes allow the delayed relaxation into a long-living coherent ground state. Aside from the potential routing of polariton condensate signals, the system forms an AND-type logic gate compatible with incoherent inputs. © 2013 American Physical Society. Source


Gao T.,FORTH IESL | Gao T.,University of Crete | Anton C.,Autonomous University of Madrid | Liew T.C.H.,Nanyang Technological University | And 9 more authors.
Applied Physics Letters | Year: 2015

Spin-selective spatial filtering of propagating polariton condensates, using a controllable spin-dependent gating barrier, in a one-dimensional semiconductor microcavity ridge waveguide is reported. A nonresonant laser beam provides the source of propagating polaritons, while a second circularly polarized weak beam imprints a spin dependent potential barrier, which gates the polariton flow and generates polariton spin currents. A complete spin-based control over the blocked and transmitted polaritons is obtained by varying the gate polarization. © 2015 AIP Publishing LLC. Source

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