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Obtaining active control over the dynamics of quantum-mechanical systems is a fascinating perspective in modern physics [1]. The approach of adaptive femtosecond quantum control follows the suggestion of Judson and Rabitz [2], in which a computer-controlled pulse shaper is used in combination with a learning algorithm [3] and direct feedback from the experiment to achieve coherent control over quantum-mechanical processes in an automated fashion, without requiring any model for the system's response.
Laser-optimized femtochemistry in the gas phase and liquid phase is one field in which this new technique is successfully employed [4] [5].
Structural changes of a molecule in the liquid phase have been induced by laser-optimized switching between the trans- and the cis-configuration in the photoisomerization of a cyanine dye molecule [6].
Adaptive high-harmonic XUV spectral shaping is performed by phase-only shaping of the fundamental (800 nm) driver laser pulse. A high degree of control is observed. Enhancement of single harmonics or group of harmonics as well as creation of spectral holes in the plateau region, i.e. suppression of particular harmonics, is achieved. Automated spectral shaping opens the door to XUV sub-femtosecond temporal pulse shaping [7].
References [1] T. Brixner, N.H. Damrauer, G. Gerber, In ''Adv. in At., Mol. and Opt. Phys.'', Vol. 46, pp. 1-54, Academic Press (2001); T. Brixner, G. Gerber, Chem. Phys. Chem. 4, 418-438 (2003) [2] R. S. Judson and H. Rabitz, Phys. Rev. Lett. 68, 1500 (1992) [3] T. Baumert, T. Brixner, V. Seyfried, M. Strehle, and G. Gerber, Appl. Phys. B 65, 779 (1997) [4] A. Assion, T. Baumert, M. Bergt, T. Brixner, B. Kiefer, V. Seyfried, M. Strehle, G. Gerber, Science 282, 919(1998); T. Brixner, N.H. Damrauer, G. Krampert, P. Niklaus, G. Gerber, J. Mod. Opt. 50, 539 (2003) [5] T. Brixner, N. H. Damrauer, P. Niklaus, and G. Gerber, Nature, Vol. 414, 57 (2001); T. Brixner, N. H. Damrauer, B. Kiefer, and G. Gerber, J. Chem. Phys. 118, 3692 (2003) [6] G. Krampert, P. Niklaus, P. Nürnberger, G. Vogt and G. Gerber, Phys. Rev. Lett. 94, Nr. 130, 0683051-4 (2005) [7] T. Pfeifer et al, Appl. Phys. B 80, 277-280 (2005) |