Berlin 2001 – scientific programme
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Q: Quantenoptik
Q 29: Application of Short Pulses II
Q 29.3: Talk
Thursday, April 5, 2001, 18:15–18:30, H 2013
Rotational wave packets observed via coherent pulse propagation — •G. Torosyan1, S. Marzenell1, J. Arlt2, and R. Beigang1 — 1Fachbereich Physik, Universität Kaiserslautern, Erwin-Schrödinger-Str., 67663 Kaiserslautern — 2School of Physics & Astronomy, University of St. Andrews, St. Andrews, KY16 9SS, Scotland
Coherent pulse propagation of mid infrared femtosecond pulses in molecular vapours was investigated. The coherent excitation of a whole manifold of rotational transitions in CO and N2O vapour led to the formation of rotational wave packets. The reshaped pulse after passage through the molecular vapour consists of a series of echoes displaying the dispersive properties of the medium and the dynamics of the rotational wave packets. The pulse reshaping und thus the dynamics of the rotational packets is strongly influenced by the spectral overlap between the absorption bands of the molecule and the spectrum of the femtosecond pulse. The experimental set-up basically consists of a cascaded OPO system generating 300 fs long idler pulses tunable between 4 µm and 8 µm. The shape of the idler pulses after transmission through a gas cell at different pressures was determined by means of a cross correlation with pulses from the Ti:Sa pump laser. The pulse reshaping was measured for different spectral overlaps between the absorption bands (P and R branch of CO and N2O) and the spectral width of the mid ir pulses at various pressures. The experimental results were compared with numerical simulations and good agreement was found.