Optical Sciences

Biomolecules and nanostructures

The Optical Sciences group studies the interaction of light and matter at the nanoscale. We do this by exploring ways to shape light and its environment. It's what we call active and passive control. Our current focus is on the interaction of light with biomolecules and nanostructures. We are part of Twente University's Department of Science and Technology and member of the MESA+ institute.
We participate in the EU-COST actions MP1102: Coherent Raman microscopy (MicroCor) and CM1202: Supramolecular photocatalytic water splitting (PERSPECT-H2O)

  

Coherent control for spectroscopy and manipulation of biological dynamics


Wohlleben W, Buckup T, Herek JL, Motzkus M
CHEMPHYSCHEM
vol. 6 issue 5 p.850-857 MAY 2005

Motivated originally by the goal of steering a photoreaction into desired product channels, the concept of coherent control is to adopt the spectral and temporal characteristics of the excitation light to the inherent molecular resonances and dynamics, such that these can be selectively addressed and manipulated. In the lost decade, the ultrafast dynamics of many atomic and molecular quantum systems in the gas and condensed phase hove been controlled successfully. Motivations in chemistry are now 1) to perform spectroscopy by coherent control, which requires a deeper understanding of control mechanisms, 2) to treat more complex, biological photoreactions, and 3) the pragmatic use of coherent control techniques, for example, for pulse compression or enhanced contrast in multiphoton microscopy. As examples for 1) and 2) we review here the combined effort and interplay of conventional spectroscopy and coherent control experiments, applied to the energy flow in the light-harvesting complex LH2 from bacterial photosynthesis. Closed-loop control experiments allowed the characteristic coupling frequency of internal conversion in the carotenoid in LH2 to be extracted. Open-loop three-pulse control experiments, on the other hand, could directly observe an anticipated Raman-excited carotenoid ground state. As a variant of difference spectroscopy, coherent control has thus served to gain complementary spectroscopic knowledge about the energy flow in carotenoids by comparing natural to manipulated dynamics. Finally, we propose future coherent control experiments on the electronic state structure of carotenoids and discuss prospects of coherent control for other biological chromophores.
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