Hannover 2010 – wissenschaftliches Programm

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A: Fachverband Atomphysik

A 20: Atomic Clusters III (with MO)

A 20.2: Hauptvortrag

Donnerstag, 11. März 2010, 14:30–15:00, F 303

Surface Quantum Optics: from Casimir-Polder forces to optical near-fields — •Sebastian Slama — Physikalisches Institut, Tübingen, Germany

Surface Quantum Optics is a new field of physics which combines ultracold atoms with solid surfaces. Such systems show very interesting features like for example the occurrence of Casimir Polder forces by which the atoms are typically attracted towards the surface. The attraction between surface and atom is based on the interaction of fluctuating dipoles, which are excited mainly by electric vacuum field fluctuations. Such forces are one of the few examples where the vacuum energy leads to measurable effects and therefore can be used for tests of QED. Measurements of Casimir-like forces have gained enormous interest in the last few years. Our group recently directly measured the Casimir-Polder force in the so-called transition regime. This was achieved by balancing the unknown surface potential with the known dipole potential of an evanescent wave. Such potentials are steep enough to compensate Casimir forces at distances of only a few hundred nanometers from the surface. Even smaller distances could be reached when the optical near-field is enhanced by surface plasmon resonances. These are collective excitations of electrons in a thin metal film on the surface. By structuring the metal film the optical near field can also be shaped in the transverse direction above the surface. This technique allows generating optical nanopotentials for nano-traps and elements for atom-optics on the surface.