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Q: Fachverband Quantenoptik und Photonik

Q 50: Poster Ultrakalte Atome

Q 50.24: Poster

Thursday, March 13, 2008, 16:30–19:00, Poster C2

Spectroscopy of two-photon resonances in a single-atom-cavity system — •Alexander Kubanek, Ingrid Schuster, Andreas Fuhrmanek, Thomas Puppe, Pepijn Pinkse, Karim Murr, and Gerhard Rempe — Max-Planck-Institut für Quantenoptik, Hans-Kopfermann-Str. 1, 85748 Garching

Strong coupling of a single atom to a single mode of an optical cavity leads to an energy level structure consisting of a ladder of doublets, the lowest of which is known as the normal-mode splitting. Here we show additional resonances in the transmission spectrum stemming from multi-photon transitions to higher doublets, which exhibit a nonlinear response to a change of probe intensity. To explain the details of the spectra, we need to take into account the micromotion of the atom which is localized in the mode by means of an auxiliary intracavity dipole trap. For this reason, we perform Monte-Carlo simulations on the dynamics of a trapped atom in a driven cavity. We calculate atomic trajectories by combining the Langevin equation of motion for the atom’s center of mass with the internal dynamics of a two-state atom coupled to a quantized mode. In this way, we are able to match theory and experiment. Additionally, we show that a classical treatment of the field following Maxwell’s equations fails to reproduce the data, regardless of whether the atom is modelled as a harmonic oscillator or as a two-state particle. This shows that the observed nonlinearity cannot be attributed to saturation effects, but is of quantum origin.