Nanofiber-based optical trapping of cold neutral atoms

We present experimental techniques and results related to the optimization and characterization of our nanofiber-based atom trap [Vetsch et al., Phys. Rev. Lett. 104, 203603 (2010)]. The atoms are confined in an optical lattice which is created using a two-color evanescent field surrounding the optical nanofiber. For this purpose, the polarization state of the trapping light fields has to be properly adjusted. We demonstrate that this can be accomplished by analyzing the light scattered by the nanofiber. Furthermore, we show that loading the nanofiber trap from a magneto-optical trap leads to sub-Doppler temperatures of the trapped atomic ensemble and yields a sub-Poissonian distribution of the number of trapped atoms per trapping site

A Nanofiber-Based Optical Conveyor Belt for Cold Atoms

We demonstrate optical transport of cold cesium atoms over millimeter-scale distances along an optical nanofiber. The atoms are trapped in a one-dimensional optical lattice formed by a two-color evanescent field surrounding the nanofiber, far red- and blue-detuned with respect to the atomic transition. The blue-detuned field is a propagating nanofiber-guided mode while the red-detuned field is a standing-wave mode which leads to the periodic axial confinement of the atoms. Here, this standing wave is used for transporting the atoms along the nanofiber by mutually detuning the two counter-propagating fields which form the standing wave. The performance and limitations of the nanofiber-based transport are evaluated and possible applications are discussed

Late Little Ice Age palaeoenvironmental records from the Anzali and Amirkola Lagoons (south Caspian Sea): Vegetation and sea level changes

This is a postprint version of the article. The official published article can be found from the link below - Copyright @ 2011 Elsevier Ltd.Two internationally important Ramsar lagoons on the south coast of the Caspian Sea (CS) have been studied by palynology on short sediment cores for palaeoenvironmental and palaeoclimatic investigations. The sites lie within a small area of very high precipitation in a region that is otherwise dry. Vegetation surveys and geomorphological investigations have been used to provide a background to a multidisciplinary interpretation of the two sequences covering the last four centuries. In the small lagoon of Amirkola, the dense alder forested wetland has been briefly disturbed by fire, followed by the expansion of rice paddies from AD1720 to 1800. On the contrary, the terrestrial vegetation reflecting the diversity of the Hyrcanian vegetation around the lagoon of Anzali remained fairly complacent over time. The dinocyst and non-pollen palynomorph assemblages, revealing changes that have occurred in water salinity and water levels, indicate a high stand during the late Little Ice Age (LIA), from AD < 1620 to 1800–1830. In Amirkola, the lagoon spit remained intact over time, whereas in Anzali it broke into barrier islands during the late LIA, which merged into a spit during the subsequent sea level drop. A high population density and infrastructure prevented renewed breaking up of the spit when sea level reached its maximum (AD1995). Similar to other sites in the region around the southern CS, these two lagoonal investigations indicate that the LIA had a higher sea level as a result of more rainfall in the drainage basin of the CS.The coring and the sedimentological analyses were funded by the Iranian National Institute for Oceanography in the framework of a research project entitled “Investigation of the Holocene sediment along the Iranian coast of Caspian Sea: central Guilan”. The radiocarbon date of core HCGL02 was funded by V. Andrieu (Europôle Méditerranéen de l'Arbois, France) and that of core HCGA04 by Brunel University

Wechselwirkung und Manipulation von an einer Nanofaser gefangenen Atomen mit Spin-Bahn gekoppeltem Licht

Abweichender Titel laut Übersetzung der Verfasserin/des VerfassersZsfassung in dt. SpracheLicht wird meistens als elektromagnetische Welle beschrieben, die bezüglich ihrer Ausbreitungsrichtung transversal polarisiert ist. Diese Beschreibung ist für Lichtfelder, die lateral stark eingeschlossen sind aber nicht mehr zutreffend. Solche Lichtfelder weisen eine longitudinale Komponente in ihrem elektrischen Feld auf. Wenn dies der Fall ist, sind Spin- und Bahndrehimpuls des Lichtfeldes gekoppelt. Sie sind damit keine voneinander unabhängigen Größen mehr, was dazu führt, dass zum Beispiel der lokale Spindrehimpuls von der Ausbreitungsrichtung des Lichtfeldes abhängt. In dieser Arbeit wird die Wechselwirkung von Atomen, die an einer Nanofaser gefangen sind, und Licht, das Spin-Bahn-Kopplung aufweist, untersucht. In unserem System wird durch die Nanofaser eine Schnittstelle zwischen neutralen Cäsium-Atomen und dem evaneszenten Feld der stark geführten optischen Moden realisiert. Mit Hilfe einer optischen Zweifarben-Falle, die auf Dipolkräften beruht, sind die Atome nahe der Oberfläche der Nanofaser in zwei diametral gegenüberliegenden Reihen gefangen. Die besondere Polarisation des evaneszenten Feldes ermöglicht es, die beiden atomaren Ensembles gleichzeitig durch optisches Pumpen in unterschiedliche Zeeman-Zustände zu bringen. In dieser Arbeit wird außerdem gezeigt, dass die zustandsabhängige Verschiebung der Energieniveaus, die durch fiktive Magnetfelder induziert wird, von der räumlichen Position der Atome abhängt. Dies ermöglicht die unabhängige und kohärente Manipulation der beiden atomaren Ensembles mit Mikrowellenstrahlung. Photonen, die von den Atomen gestreut werden, koppeln durch die Spin-Bahn-Wechsel-wirkung von Licht unterschiedlich stark an Moden, die sich in entgegengesetzter Richtung in der Nanofaser ausbreiten. Hier wird gezeigt, dass diese Asymmetrie der Streuraten in die beiden Ausbreitungsrichtungen höher als 10:1 sein kann. Die Asymmetrie kann man abhängig von der Polarisation des anregenden Lichtfeldes sowie des inneren Zustandes der Atome beeinflussen. Hinzu kommt, dass die Spin-Bahn-Wechselwirkung von Licht in unserem System dazu führen kann, dass Lichtfelder abhängig von ihrer Ausbreitungsrichtung durch die Nanofaser unterschiedlich stark transmittiert werden. Basierend auf diesem Effekt wird gezeigt, dass eine optische Diode im Nanomaßstab realisiert werden kann, die auch mit einzelnen Photonen noch funktioniert.Light is often described as an electromagnetic wave that is transversely polarized with respect to its propagation direction. This description however breaks down when the light field is strongly transversely confined. Such a light field exhibits a longitudinal component of its electro-magnetic field. In this situation the spin and the orbital angular momentum of light are coupled and thus not independent quantities anymore, e.g., the local spin depends on the propagation direction of the light field. In this thesis, the interaction between nanofiber-trapped atoms and spin-orbit coupled light fields is studied in the dispersive and the resonant regime. In our system, the nanofiber provides an evanescent field interface between the strongly guided optical mode and neutral cesium atoms. The atoms are confined in two diametric arrays in the vicinity of the nanofiber surface using a nanofiber-based two-color optical dipole trap. It is demonstrated that by using the peculiar polarization pattern of the guided light fields, the two atomic ensembles can be simultaneously optically pumped to opposite Zeeman states. Furthermore, it is shown that the state-dependent light shifts induced by a fictitious magnetic field can be locally distinct. This enables the independent coherent manipulation of the two ensembles via microwave radiation. Moreover, due to the spin-orbit interaction of light, the system exhibits asymmetric scattering of photons by the atoms into counter-propagating nanofiber-guided modes. An asymmetry of the scattering rates into the two propagation directions higher than 10:1 is demonstrated. It is presented that this asymmetry can be tailored by the internal state of the atom and the polarization of the excitation light field. Additionally, it is shown that the spin-orbit interaction in our system can lead to nonreciprocal transmission of a nanofiber-guided light field. Building on this property a nanoscale optical diode is demonstrated, which can be operated down to the single-photon regime.13