Hannover 2013 – wissenschaftliches Programm

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A: Fachverband Atomphysik

A 39: Poster: Atomic systems in external fields

A 39.10: Poster

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

Dynamic phase studies at EIT conditions in thermal rubidium — •Stephan Welte — Physikalisches Institut Uni Freiburg

We investigate the response of an EIT medium to changes of the magnetic field vector. Employing two phase locked external cavity diode lasers, we prepare the atoms in a dark superposition of two Rb ground states, (F=1, mF=-1) and (F=2, mF=1). During preparation of the dark state a constant magnetic field is employed as quantization axis. Its magnitude is chosen as the magic 3.2 Gauss where ground state transition is magnetic-field insensitive in the first-order Zeeman effect. Applying a second magnetic field in the same direction as the quantization field results in a small Zeeman shift of the two mF states. When returning to the original field, the two states of the superposition have picked up unequal dynamical phases due to the quadratic Zeeman effect. As a result, there is a relative phase change in the superposition state which manifests itself in a rise of the absorption signal. We compare our findings with numerical simulations using a realistic eight-level density matrix. A further experiment in progress concerns the detection of a Berry phase imposed in a thermal EIT medium. By rotating an additonal magnetic field in a cone and returning to the original field, the two mF levels of the dark state will acquire different Berry phases which depend on the cone angle. As in the dynamic phase experiment, a relative phase difference should manifest itself in a rise of the absorption signal. This feature is also predicted in our numerical simulation.