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Q: Quantenoptik

Q 44: Poster: Ultrakurzer Lichtimpulse

Q 44.6: Poster

Donnerstag, 27. März 2003, 16:30–18:30, Lichthof

Coherent excitation of two-photon transitions in sodium — •Sabine Stock^1,2, Jerome Degert¹, Beatrice Chatel¹, and Bertrand Girard¹ — ¹Laboratoire Collisions Agregats Reactivité, IRSAMC, Université Paul Sabatier, 118 route de Narbonne, 31062 Toulouse, France — ²Laboratoire Kastler Brossel, ENS, 24 rue Lhomond, 75005 Paris, France

We have studied coherent excitation of two-photon transitions in sodium (3s → 3p → 4d, 5s) induced by chirped ultrashort laser pulses, observing interferences between different quantum paths leading to the final state.

These interferences result in oscillations in the final state amplitude with regard to the chirp rate. They were studied for positive (state 4d) as well as for negative (state 5s) chirp of the femtosecond pulses. Thereby the contrast of the oscillations in state 5s is much bigger than in state 4d, due to the ratio of the dipole moments involved in the transition. The influence of higher order chirp in the pulses was also studied experimentally and theoretically. It was found to cause much more complex shapes of the excited state amplitude.

A possible application of these results is the use of chirped femtosecond pulses in polychromatic artificial guide star projects, being developed for improvement in adaptive optics. To test the feasibility of this application, computer simulations were carried out.