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DPG

Berlin 2001 – scientific programme

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Q: Quantenoptik

Q 17: Poster: Cooling and Trapping

Q 17.26: Poster

Wednesday, April 4, 2001, 12:30–15:00, AT2

Modulation techniques in a molecular Ramsey-Bordé interferometer — •Christian Lisdat, Matthias Frank, Horst Knöckel, and Eberhard Tiemann — SFB 407, Institut für Quantenoptik, Universität Hannover

On the example of a matter wave interferometer with K2 molecules, we present different methods to simplify the observed interference structures superimposed on a spectral line split up by hyperfine interaction. The interferometer is of the Ramsey-Bordé type and uses transitions from the ground state X 1Σg+ to the state b 3Πu (0+).
The experiments were performed in the framework of investigations of collisions between K2 molecules and potassium atoms within the interferometer. The aim is to improve the accuracy of measuring the phase of the interference pattern, which contains the information about the collision process.
We consider optical pumping by additional laser fields for the depletion of population of some ground state hyperfine levels to prepare a quantum state, that leads to non-blending transitions in the interferometer.
In connection with lock-in technique amplitude modulation as well as frequency modulation of laser beams of the interferometer is investigated to subtract or reduce the incoherent envelope of one or several interference patterns. The influence of amplitude modulation of the depletion laser and lock-in detection is discussed as well.
As follow-up treatment digital filtering is demonstrated, which uses a Fourier transform high-pass filter to separate the interference patterns from the envelope of the spectral line.

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