Hamburg 2009 – scientific programme

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Q: Fachverband Quantenoptik und Photonik

Q 55: Poster III

Q 55.49: Poster

Thursday, March 5, 2009, 16:30–19:00, VMP 8 Foyer

High order transverse modes in a Fabry-Perot cavity - Beyond the paraxial approximation — •Markus Koch, Martin Zeppenfeld, Borys Hagemann, Michael Motsch, Pepijn Pinkse, and Gerhard Rempe — Max-Planck-Institut für Quantenoptik, Hans-Kopfermann-Str. 1, 85748 Garching

Many interesting effects have been observed, when atoms or molecules are coupled to the modes of an optical cavity. Among them cavity cooling has attracted a lot of attention over the last years, since it promises to cool atoms or molecules without the need for a closed cycling transition. For best cooling a cavity with as many as possible degenerate transversal modes is needed.
We have performed high-precision measurements on the spectrum of the transverse modes of a high-finesse Fabry-Perot cavity. We find that the degeneracy of high Laguerre-Gaussian modes, predicted by the paraxial approximations, is lifted. Taking into account corrections beyond the paraxial approximation, we can quantitatively describe the splitting. We also observe two distinct sets of modes which indicates a coupling between the orbital and the spin angular momentum of light within the cavity.
Apart from the theoretical appeal, these new insights into the mode spectrum of a high-finesse cavity will be important for the design of non-spherical cavity mirrors to recover the mode degeneracy.