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Search Results: 1 - 10 of 91890 matches for " Philippe W. Courteille "
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Optical parametric oscillation with distributed feedback in cold atoms
Alexander Schilke,Claus Zimmermann,Philippe W. Courteille,William Guerin
Physics , 2011, DOI: 10.1038/nphoton.2011.320
Abstract: There is currently a strong interest in mirrorless lasing systems, in which the electromagnetic feedback is provided either by disorder (multiple scattering in the gain medium) or by order (multiple Bragg reflection). These mechanisms correspond, respectively, to random lasers and photonic crystal lasers. The crossover regime between order and disorder, or correlated disorder, has also been investigated with some success. Here, we report one-dimensional photonic-crystal lasing (that is, distributed feedback lasing) with a cold atom cloud that simultaneously provides both gain and feedback. The atoms are trapped in a one-dimensional lattice, producing a density modulation that creates a strong Bragg reflection with a small angle of incidence. Pumping the atoms with auxiliary beams induces four-wave mixing, which provides parametric gain. The combination of both ingredients generates a mirrorless parametric oscillation with a conical output emission, the apex angle of which is tunable with the lattice periodicity.
Photonic Band Gaps in One-Dimensionally Ordered Cold Atomic Vapors
Alexander Schilke,Claus Zimmermann,Philippe W. Courteille,William Guerin
Physics , 2011, DOI: 10.1103/PhysRevLett.106.223903
Abstract: We experimentally investigate the Bragg reflection of light at one-dimensionally ordered atomic structures by using cold atoms trapped in a laser standing wave. By a fine tuning of the periodicity, we reach the regime of multiple reflection due to the refractive index contrast between layers, yielding an unprecedented high reflectance efficiency of 80%. This result is explained by the occurrence of a photonic band gap in such systems, in accordance with previous predictions.
Cavity-Controlled Collective Scattering at the Recoil Limit
Simone Bux,Christine Gnahm,Reinhardt A. W. Maier,Claus Zimmermann,Philippe W. Courteille
Physics , 2011, DOI: 10.1103/PhysRevLett.106.203601
Abstract: We study collective scattering with Bose-Einstein condensates interacting with a high-finesse ring cavity. The condensate scatters the light of a transverse pump beam superradiantly into modes which, in contrast to previous experiments, are not determined by the geometrical shape of the condensate, but specified by a resonant cavity mode. Moreover, since the recoil-shifted frequency of the scattered light depends on the initial momentum of the scattered fraction of the condensate, we show that it is possible to employ the good resolution of the cavity as a filter selecting particular quantized momentum states.
Collective Atomic Recoil Lasing and Superradiant Rayleigh Scattering in a high-Q ring cavity
Sebastian Slama,Gordon Krenz,Simone Bux,Claus Zimmermann,Philippe W. Courteille
Physics , 2007, DOI: 10.1063/1.2839129
Abstract: Cold atoms in optical high-Q cavities are an ideal model system for long-range interacting particles. The position of two arbitrary atoms is, independent on their distance, coupled by the back-scattering of photons within the cavity. This mutual coupling can lead to collective instability and self-organization of a cloud of cold atoms interacting with the cavity fields. This phenomenon (CARL, i.e. Collective Atomic Recoil Lasing) has been discussed theoretically for years, but was observed only recently in our lab. The CARL-effect is closely linked to superradiant Rayleigh Scattering, which has been intensely studied with Bose-Einstein condensates in free space. By adding a resonator the coherence time of the system, in which the instability occurs, can be strongly enhanced. This enables us to observe cavity-enhanced superradiance with both Bose-Eisntein condensed and thermal clouds and allows us to close the discussion about the role of quantum statistics in superradiant scattering.
The role of Mie scattering in the seeding of matter-wave superradiance
Romain Bachelard,Helmar Bender,Philippe W. Courteille,Nicola Piovella,Christian Stehle,Claus Zimmermann,Sebastian Slama
Physics , 2012, DOI: 10.1103/PhysRevA.86.043605
Abstract: Matter-wave superradiance is based on the interplay between ultracold atoms coherently organized in momentum space and a backscattered wave. Here, we show that this mechanism may be triggered by Mie scattering from the atomic cloud. We show how the laser light populates the modes of the cloud, and thus imprints a phase gradient on the excited atomic dipoles. The interference with the atoms in the ground state results in a grating, that in turn generates coherent emission, contributing to the backward light wave onset. The atomic recoil 'halos' created by the scattered light exhibit a strong anisotropy, in contrast to single-atom scattering.
Synchronization of Bloch oscillations by a ring cavity
Marina Samoylova,Nicola Piovella,Gordon R. M. Robb,Romain Bachelard,Philippe W. Courteille
Physics , 2015,
Abstract: We consider Bloch oscillations of ultracold atoms stored in a one-dimensional vertical optical lattice and simultaneously interacting with a unidirectionally pumped optical ring cavity whose vertical arm is collinear with the optical lattice. We find that the feedback provided by the cavity field on the atomic motion synchronizes Bloch oscillations via a mode-locking mechanism, steering the atoms to the lowest Bloch band. It also stabilizes Bloch oscillations against noise, and even suppresses dephasing due to atom-atom interactions. Furthermore, it generates periodic bursts of light emitted into the counter-propagating cavity mode, providing a non-destructive monitor of the atomic dynamics. All these features may be crucial for future improvements of the design of atomic gravimeters based on recording Bloch oscillations.
Coherence effects in scattering order expansion of light by atomic clouds
Mohamed-Taha Rouabah,Marina Samoylova,Romain Bachelard,Philippe W. Courteille,Robin Kaiser,Nicola Piovella
Physics , 2014, DOI: 10.1364/JOSAA.31.001031
Abstract: We interpret cooperative scattering by a collection of cold atoms as a multiple scattering process. Starting from microscopic equations describing the response of $N$ atoms to a probe light beam, we represent the total scattered field as an infinite series of multiple scattering events. As an application of the method, we obtain analytical expressions of the coherent intensity in the double scattering approximation for Gaussian density profiles. In particular, we quantify the contributions of coherent backward and forward scattering.
Direct Measurement of intermediate-range Casimir-Polder potentials
Helmar Bender,Philippe W. Courteille,Carsten Marzok,Claus Zimmermann,Sebastian Slama
Physics , 2009, DOI: 10.1103/PhysRevLett.104.083201
Abstract: We present the first direct measurements of Casimir-Polder forces between solid surfaces and atomic gases in the transition regime between the electrostatic short-distance and the retarded long-distance limit. The experimental method is based on ultracold ground-state Rb atoms that are reflected from evanescent wave barriers at the surface of a dielectric glass prism. Our novel approach does not require assumptions about the potential shape. The experimental data confirm the theoretical prediction in the transition regime.
Cavity-enhanced superradiant Rayleigh scattering with ultra-cold and Bose-Einstein condensed atoms
Sebastian Slama,Gordon Krenz,Simone Bux,Claus Zimmermann,Philippe W. Courteille
Physics , 2007, DOI: 10.1103/PhysRevA.75.063620
Abstract: We report on the observation of collective atomic recoil lasing and superradiant Rayleigh scattering with ultracold and Bose-Einstein condensed atoms in an optical ring cavity. Both phenomena are based on instabilities evoked by the collective interaction of light with cold atomic gases. This publication clarifies the link between the two effects. The observation of superradiant behavior with thermal clouds as hot as several tens of $\mu\textrm{K}$ proves that the phenomena are driven by the cooperative dynamics of the atoms, which is strongly enhanced by the presence of the ring cavity.
Spatial and temporal localization of light in two dimensions
Carlos E. Máximo,Nicola Piovella,Philippe W. Courteille,Robin Kaiser,Romain Bachelard
Physics , 2015, DOI: 10.1103/PhysRevA.92.062702
Abstract: Quasi-resonant scattering of light in two dimensions can be described either as a scalar or as a vectorial electromagnetic wave. Performing a scaling analysis we observe in both cases long lived modes, yet only the scalar case exhibits Anderson localized modes together with extremely long mode lifetimes. We show that the localization length of these modes is influenced only by their position, and not their lifetime. Investigating the reasons for the absence of localization, it appears that both the coupling of several polarizations and the presence of near-field terms are able to prevent long lifetimes and Anderson localization.
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