Hannover 2013 – wissenschaftliches Programm

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Q: Fachverband Quantenoptik und Photonik

Q 56: Poster III

Q 56.55: Poster

Donnerstag, 21. März 2013, 16:00–18:30, Empore Lichthof

ac Stark shift of a cesium atom in a two-color nanofiber-based atom trap — •Fam Le Kien, Philipp Schneeweiss, and Arno Rauschenbeutel — VCQ, TU Wien - Atominstitut, Stadionallee 2, 1020 Wien, Austria

An atom exposed to an intense far-detuned light field experiences shifts of its energy levels. In general, these light shifts (ac Stark shifts) depend not only on the dynamical polarizability of the atomic state but also on the polarization of the light field. Here, we present central results of a systematic derivation of the ac Stark shift induced by a far-off-resonance light field of arbitrary polarization. These results are in particular relevant when theoretically describing the optical trapping of atoms using near-fields or nonparaxial light beams which in general lead to nontrivial polarization patterns.

When applying this light-shift formalism to cesium atoms in a two-color nanofiber-based optical trap, we find Zeeman-state-dependent optical trapping potentials. The state dependence is a consequence of the effective magnetic field which results from the vector polarizability of the atomic ground state in conjunction with the residual ellipticity of the nanofiber-guided trapping light fields. Using an external (real) magnetic offset field, we observe a spatial displacement of the trapping potential that can be continuously controlled. We propose to exploit this behavior for microwave control and cooling of the atomic motional states. For this purpose, we calculate the Franck-Condon factors between vibrational levels and show that an implementation of these microwave operations appears experimentally feasible.