Darmstadt 2008 – scientific programme

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Q: Fachverband Quantenoptik und Photonik

Q 49: Ultrakurze Laserpulse (Anwendungen II)

Q 49.11: Talk

Thursday, March 13, 2008, 19:00–19:15, 3H

Strong-field control landscapes of coherent electronic excitation — •Tim Bayer, Matthias Wollenhaupt, and Thomas Baumert — Universität Kassel, Institut für Physik und CINSaT, Heinrich-Plett-Str. 40, D-34132 Kassel, Germany

We study physical mechanisms of resonant strong-field coherent control. To this end, time-of-flight photoelectron spectra from multi-photon ionization of potassium atoms with intense shaped femtosecond laser pulses are measured and discussed in terms of Selective Population of Dressed States (SPODS). Recently, it was shown [1,2] that pulse sequences and chirped pulses provide efficient yet complementary realizations of SPODS. Combining these two approaches thus leads to a physically motivated pulse parametrization that opens up search spaces of manageable size. The SPODS control topology of these reduced search spaces is mapped out experimentally and presented in the form of strong-field control landscapes. Having revealed the landscape topologies we apply the same pulse parametrization to an adaptive optimization procedure in order to optimize SPODS on one of the mapped parameter spaces. The concept of control trajectories is introduced and serves to visualize the temporal evolution of the optimization on the measured landscape surface. The question whether such optimization procedures under experimentally constrained conditions in fact end up at the global optimum or eventually become trapped by suboptimal local extrema [3] is addressed.

[1] M. Wollenhaupt et al.: PRA 73, 2006 [2] M. Wollenhaupt et al.: APB 82, 2006 [3] H. A. Rabitz et al.: PRA 74, 2006